Alkaline battery without mercury and electronic apparatus powered thereby

ABSTRACT

An alkaline battery comprises a negative electrode having an active material comprised of mercuryless zinc powder containing a gelling agent. In one embodiment, the alkaline battery comprises a current collector having an outermost surface coated with a layer of zinc or a metal having a hydrogen overvoltage higher than that of zinc, and an electrolyte containing one or more compounds selected from the group consisting of an indium compound, lead oxide; a hydroxide of alkaline earth metal and a surfactant having polyethylene oxide. In another embodiment, the negative electrode active material contains one or more species of materials selected from the group consisting of an indium compound, lead oxide, a hydroxide of alkaline earth metal and a surfactant having polyethylene oxide, and a current collector having an outermost surface coated with a layer of zinc or a metal having a hydrogen overvoltage higher than that of zinc. An improved alkaline battery is achieved which does not pose environmental problems, and which corrosion of the zinc powder of the battery is suppressed, and in which a good discharge performance of the battery is maintained.

This is a division of application Ser. No. 08/101,716 filed Aug. 3,1993, now abandoned.

BACKGROUND OF THE INVENTION

The present invention relates to an alkaline battery which usesmercuryless zinc powder as a negative electrode active material, anduses silver oxide, manganese dioxide, oxygen or the like as a positiveelectrode active material, and a clock or watch which uses the alkalinebattery.

Conventional alkaline batteries suffer from the drawbacks in that zincpowder used in the alkaline battery is corroded and dissolved by analkaline electrolyte solution, and in that the generation of hydrogengas and the self-discharge in battery performance accompanying therewithare large. In addition, a battery is formed by a collector such ascopper or the like which contacts with zinc, and hydrogen gas has beenalso generated therefrom. In the prior art, as a countermeasure toprevent the above, zinc is mercurated with mercury having a highhydrogen overvoltage, or zinc oxide is added to an electrolyte solutionup to approximate saturation.

However, environmental pollution due to mercury from used dry batterieshas become a problem in recent years, and various studies for reducingmercury have been performed. Among processes undertaken during thestudies are the formation zinc alloys, plating of a collector, andaddition of an organic or inorganic inhibitor to an electrolytesolution.

The formation of zinc alloys has been performed for a fairly long time,and metals such as bismuth, indium, lead and the like have beeninvestigated. Many patent applications pertaining to this process havebeen also filed, for example, Japanese Patent Publication No. 25-27822(1950), Japanese Patent Publication No. 33-3204 (1958), Japanese PatentPublication No. 63-3942 (1988), and Japanese Patent ApplicationLaid-Open No. 1-10861 (1989).

As the inorganic inhibitor, indium oxide and indium hydroxide as theindium compound have been frequently studied, and many patentapplications have been also filed, including for example, JapanesePatent Publication No. 51-36450 (1976), Japanese Patent ApplicationLaid-Open No. 49-93831 (1974), Japanese Patent Application Laid-Open No.49-112125 (1974), Japanese Patent Application Laid-Open No. 59-186255,Japanese Patent Application Laid-Open No. 59-186256 (1984), and JapanesePatent Application Laid-open No. 4-26061 (1992). The use of a compoundof alkaline earth metal as the inorganic inhibitor is addressed inJapanese Patent Application Laid-Open No. 49-8727 (1974), JapanesePatent Application Laid-Open No. 49-93831 (1974), and Japanese PatentApplication Laid-Open No. 49-121926 (1974). The use of organicinhibitors is addressed in Japanese Patent Application Laid-Open No.2-86064 (1990), and Japanese Patent Application Laid-Open No. 3-29270(1991).

On the other hand, with respect to the process of plating a collector,the surface has been coated with indium or tin having a high hydrogenovervoltage by means of a method of plating or the like, and theformation of a battery due to the contact with zinc is prevented so asto suppress the generation of hydrogen. Such process is addressed inJapanese Patent Application Laid-Open No. 52-74834 (1977), JapanesePatent Application Laid-Open No. 52-98929, Japanese Patent ApplicationLaid-Open No. 60-221958 (1985), and Japanese Patent Publication No.52-42211 (1977).

In the prior art, investigation has been made as to each individualtechnique as described above, however, because the strong anticorrosionagent mercury has been used, optimization by combination of thecharacteristics of each technique has not been frequently performed.

Mercury, which is added in order to prevent corrosion and dissolution ofzinc, is not only expensive from a viewpoint of cost, but is alsoassociated with the problem of environmental pollution. In addition, theaddition of zinc oxide also includes such a task that the viscosity ofthe electrolyte is raised, and the conductivity is lowered.

Indium oxide and indium hydroxide as the inorganic inhibitor alsoincludes many problems.

Indium oxide is extremely difficult to dissolve in the electrolytesolution which is a caustic alkali, and hydrogen gas is consequentlygenerated due to the contact of indium oxide with zinc powder or thecollector. This is considered to be due to the fact that the solubilityof indium oxide is poor, it is impossible to supply indium ion of adegree to sufficiently coat the zinc surface and the collector surface,and indium oxide becomes conductive due to inevitable impurities duringproduction contacts with zinc and the collector, resulting in formationof a local battery.

It is said that as compared with indium oxide, indium hydroxide to someextent dissolves in an electrolyte solution of caustic alkali, and itssolubility relates to the size and crystallinity of particles. However,as compared with indium compounds such as indium sulfate, indiumsulfamate, indium chloride and the like, it is extremely difficult todissolve. Thus, the same problems are associated as with of indiumoxide. In addition, indium as an amphoteric compound generates polyiontogether with hydroxide ion (those similar to the description inInorganic Chemistry Series 7, Coordinate Stereochemistry, written byYoichi NIIMURA, published by Baihukan Co. Ltd., 65-66), and increasesthe viscosity of the electrolyte solution, so that it lowers theconductivity of the electrolyte solution and deteriorates batteryperformance.

Considerable advantageous effects are appreciated in the use of theindium compound as the inhibitor which is easier to dissolve in theelectrolyte solution as compared with the case in which the conventionalscarcely soluble inhibitor is used. However, in order to further utilizethe characteristic of the indium compound, it is necessary to also solveproblems as follows.

The electrode potential of zinc is lower than the deposition potentialof indium, so that when indium ion is present in the electrolyte, indiumis deposited as metal on zinc and the collector contacting with zinc.However, hydrogen generation is accompanied as a competitive reaction inaccordance with the deposition reaction of indium, and this has been thecause of deficiencies such as liquid leakage and expansion of thealkaline battery. In addition, there has been such a problem that indiumion which is not deposited precipitates as hydroxide and decreases theconductivity of the electrolyte solution.

Other than the indium compound, compounds of metals having a relativelyhigh hydrogen overvoltage such as tin and lead are used as theinhibitor, however, there have been problems as follows.

Metal ion, which is supplied from the metal compounds of these metals tothe electrolyte solution, is reduced on the surface of zinc and thecollector, and deposited as metal. However, when the surface is coatedwith one species of metal, crystal grains become coarse, it isimpossible to homogeneously coat the surface, and the effect is reduced.It is difficult to suppress the hydrogen generation and improve thedischarge characteristic by means of a single metal. In addition, thecompounds of indium and the like are expensive, so that the use of onlyone species becomes expensive from a viewpoint of cost.

With respect to the corrosion and dissolution of zinc, there isconsidered a case in which zinc itself is corroded by water and thehydroxyl group in the alkaline solution, and a case in which a localbattery is formed by the contact with metals such as copper, brass andthe like of the collector which are nobler than zinc resulting indissolution. Thus, attempts have been frequently made to add a metalhaving a high hydrogen overvoltage to zinc to form an alloy so as tosuppress corrosion and dissolution. It is known that the effect thereofis remarkably expressed especially when indium is added. When zinc isused in which indium is added in a relatively high concentration by, forexample, not less than 400 ppm, a part of indium and zinc is oncedissolved by the contact with copper and the like of the collector. Itis considered that the corrosion and dissolution of zinc are suppressedby a mechanism that the dissolved indium ion is then deposited on thecollector, and a film of indium is formed on the collector. However,there has been such a problem that the amount of indium ion to bereduced on the collector is extremely small in the initial state of thecontact between zinc and the collector so that hydrogen is reduced andhydrogen gas is generated.

An attempt has been made to suppress the corrosion and dissolution ofzinc and the collector using a compound of metal nobler than zinc as theinhibitor. However, in the case of conventional zinc in which there areimpurities such as iron, it is necessary to use a large amount of theinhibitor, and it has been impossible to suppress the corrosion anddissolution of zinc unless, for example, large amount of lead monoxide,which is a non-pharmaceutical harmful substance and may causeenvironmental pollution, is used. Further, there has also been such aproblem that when large amounts of lead monoxide and an indium compoundare added, needle-like crystals are deposited which break through aseparator to cause a short circuit.

In recent applications, mercurated zinc has been used in a coin orbutton type silver oxide battery which prevents hydrogen gas generationand self-discharge of the battery.

In recent years, efforts have been made to improve the additives used inzinc powder, the separators, the sealing agents, the gelling agents andthe elimination of mercury for cylindrical alkaline batteries. However,in the case of a coin or button-type silver oxide battery in which thereis no escape for the hydrogen gas due to the structure of the battery,there are problems such as the occurrence of expansion and liquidleakage due to gas pressure, self-discharge of the battery and achievingthe elimination of mercury.

The foregoing describes problems associated with conventional inhibitorsand the amount of water in the battery. Although improvements withconventional inhibitors has resulted in improvements in thecharacteristics of the alkaline battery, it has not been possible toachieve the effective removal of mercury. Further, improvements thereofwill be described hereinafter.

When only a conventional inorganic inhibitor is used, such problemsarise in that the inhibitor is not homogeneously distributed on thecollector because of a fairly small amount of the electrolyte solutionin an actual battery and no metal coating is given, and bubbles generatebetween a negative electrode combined agent and the collector.

The manufacture of the collector using a metal such as indium or tin, orplating the collector with these metals is fairly effective in solvingthe above described problems.

However, when tin is used, although it is possible to suppress thehydrogen gas generation as compared with a case in which a collector ofcopper is used, no effect of a degree equivalent to the case of the useof mercury has been obtained.

When indium is used, although the effect is certainly larger than thatof tin, there has been such a problem that the raw material isexpensive, thus increasing the manufacturing cost. In the case of indiumplating, there have been such problems that the application process ispoor, no homogeneous film is provided, impurities remain on the surface,and the effect is weakened.

In addition, when no inhibitor is used and the collector is only coatedwith a metal, there has been such a problem that a countermeasure isinsufficient for preventing hydrogen gas formation.

Further, it has been impossible to ensure sufficient preventionself-discharge even when fluorocarbon/polyoxyethylene series,polyoxyethylene alkylamide and the like are used which are organicinhibitors considered to be effective in the prior art.

Namely, it has been found that there is such a problem that nosufficient effect is obtained using each of the corrosion preventingmethods in the prior art. As a result of reconsideration of the role ofeach inhibitor, it has been found that better effects are obtained byusing a collector coated with zinc or a metal having a hydrogenovervoltage higher than that of zinc, together with the use of variousinhibitors.

When a higher battery capacity is desired, a decrease in the batterycapacity due to the absence of mercury must be compensated. In the caseof a cylindrical alkaline dry battery, it is desired to increase thequantity of zinc powder as the active material. However, there has beensuch a problem that in the case of the button-type or coin-type alkalinebattery in which there is no room from a viewpoint of.space, suchaccomplishment is almost impossible.

On the other hand, in a clock or watch which uses an alkaline batterycontaining mercury, the battery containing mercury is recovered atretail stores in the case of a battery exchange. However, there has beensuch a problem that when the main body of the clock or watch isdiscarded, the mercury which is also discarded contributes toenvironmental pollution. Particularly with the continuing decrease inprice of clocks and watches, there is the possibility that the number ofclocks or watches to be discarded due to the service life expiration ofthe batteries increases.

SUMMARY OF THE INVENTION

An object of the present invention is to provide an alkaline batterywhich does not contain mercury.

Another object of the present invention is to provide an alkalinebattery comprising mercuryless zinc powder as a negative electrodeactive material.

Still another object of the present invention is to provide an apparatususing an alkaline battery which does not contain mercury.

A further object of the present invention is to provide an apparatususing an alkaline battery comprising mercuryless zinc powder as anegative electrode active material.

When an indium compound such as indium sulfate, indium sulfamate, indiumchloride or the like is added as an inhibitor into an electrolytesolution or a negative electrode active material, so as to allow indiumion to exist in the electrolyte solution in an amount sufficient to coatzinc and the collector, indium can be immediately deposited on zinc andthe negative electrode collector. By coating the zinc and the collectorwith indium having a high hydrogen overvoltage, it is possible toprevent corrosion and dissolution of the two.

Further, in order to effectively utilize these inhibitors, a complexingagent is added into the electrolyte solution beforehand, and indium ionwhich is generated by dissolution of the indium compound is subjected tocomplexing. Thus it is possible to prevent hydrogen gas formation duringdeposition of indium and the decrease in the conductivity of theelectrolyte solution due to precipitation of indium which is notdeposited as a hydroxide.

The problem caused by the use of the inhibitor of only one species ofthe compound of metal can be solved by adding two or more species ofcompounds selected from an indium compound, a tin compound containingtetravalent tin and lead oxide into the electrolyte solution or thenegative electrode active material, and depositing metal contained inthese compounds as an allow onto zinc and the negative electrodecollector. Characteristics, which cannot be obtained by a single metalcoating, are obtained by depositing the two or more species of metals.

When zinc in which indium is added in a relatively high concentration isused, it is considered that the corrosion and dissolution of zinc or thecollector are suppressed owing to a mechanism that indium ion dissolvedfrom zinc is deposited on the collector, and a film of indium is formedon the collector. However, in the initial stage of the contact betweenzinc and the collector, the amount of indium ion to be reduced on thecollector is extremely small. Thus, when the one or more species of thecompounds selected from the indium compound which is nobler than zinc,the tin compound containing tetravalent tin and lead oxide are added asthe inhibitor into the electrolyte solution or the negative electrodeactive material, and the meatal ion is allowed to exist in theelectrolyte solution in an amount sufficient to coat zinc and thecollector, then it is possible to immediately deposit lead onto zinc andthe negative electrode collector, and it is possible to suppress thegeneration of hydrogen. In this case, depending on the amount of theinhibitor is about 10-1000 ppm with respect to the zinc powder. If theadding amount is small, it is impossible to sufficiently coat zinc andthe collector, while if the adding amount is too large, there is such abad effect that needle-like crystals penetrate through a separator tocause a short circuit.

When mercuryless zinc powder in which the content of iron is not morethan 4 ppm with respect to a weight of zinc is used, one or more speciesof compounds selected from an indium compound nobler than zinc, a tincompound containing tetravalent tin and lead oxide are added as theinhibitor into the electrolyte solution or the negative electrode activematerial, and ion is allowed to exist in the electrolyte solution in anamount sufficient to coat zinc and the collector, then it is possible toimmediately deposit a coating film of metal which is nobler than zinc onzinc and the negative electrode collector, and it is possible tosuppress the corrosion and dissolution of zinc and the hydrogengeneration accompanying therewith. In this case, it is preferable thatthe adding amount of the inhibitor be about 10-1000 ppm with respect tothe zinc powder. If the adding amount is too small, it is impossible tosufficiently coat zinc and the collector, and there is such a bad effectthat needle-like crystals penetrate through a separator to cause a shortcircuit.

Using mercuryless zinc containing at least one species of metals ofgallium, indium, lead, bismuth, aluminum, calcium and the like which aresaid to have an effect of increasing the hydrogen overvoltage and aneffect of adjusting the particle shape during manufacturing of particlesas the negative electrode active material, in the case of an electrolytesolution of the potassium hydroxide type, the amount of water in thebattery is 0.31-0.57 mg (or 0.31-0.57 μL at ordinary temperature) per aweight of 1 mg of mercuryless zinc, or in the case of an electrolytesolution of sodium hydroxide type, the amount of water in the battery is0.32-0.59 mg (or 0.32-0.59 μL at ordinary temperature) per a weight of 1mg of mercuryless zinc, thereby it is possible to produce a coin orbutton type silver oxide battery in which the gas generation amount isnot more than 0.03 μL/g/day, and the self-discharge rate is not morethan 4%/year.

Further, in order to approximate the performance of the batterycontaining mercury, it is necessary to combine and use varioustechniques.

Mercuryless zinc alloy powder added with metals of indium, lead,bismuth, calcium, aluminum and the like and a gelling agent for holdingmoisture in the battery are used as a negative electrode combined agent,a collector having the outermost layer which is coated with zinc ormetal having a hydrogen overvoltage higher than that of zinc is used,and an inhibitor selected from an indium compound, lead oxide, hydroxideof alkaline earth metal, and a surfactant having polyoxyethylene groupis added into the electrolyte solution or the negative electrode activematerial, thereby it is possible to obtain a battery in which thehydrogen gas generation is less, and the electric characteristics aregood.

Especially, with respect to the coating of the collector, an alloy layercontaining zinc as an essential element and containing one or morespecies selected from indium, lead and tin as a selective element isprovided, thereby it is possible to provide an alkaline battery which isadvantageous from a viewpoint of cost and in which the hydrogen gasgeneration can be suppressed.

Further, there are such problems due to the elimination of mercury thatthe self-discharge increases and the capacity decreases. However, sincethe zinc alloy layer of the collector is made thick to some extent, itis possible to increase the capacity of the battery withoutsignificantly changing the spacing in a battery casing.

Indium compounds such as indium sulfate, indium sulfamate, indiumchloride and the like dissolve in a concentrated caustic alkalisolution, which forms alkaline complex ion capable of cathode reductionreferred to in the plating.

The alkaline complex ion of indium is subjected to zinc surfacereduction representing a potential lower than a reduction potential ofitself, and indium is immediately deposited as metal. In addition, thecollector comprised of a material such as copper or the like contactswith zinc, so that the same potential as that of zinc is obtained, andindium is deposited in the same manner. When the surfaces of zinc andthe collector are initially coated with indium, all of the surfacesachieve the same potential of indium, and the electrochemical drivingforce is lost, so that further deposition of indium is ceased. However,when the zinc surface is newly exposed by discharge, indium which existsas the alkaline complex ion is immediately reduced and deposited.

The inhibitor of the indium compound functions more effectively byadding the complexing agent. This is due to the fact that the alkalinecomplex ion of indium and hydrated indium ion are unstable, so that theyprecipitate with no complexing agent to be insoluble in the electrolytesolution, or even if they are dissolved, they precipitate as hydroxidedue to minute environmental changes, or they are apt to change into aviscous solution such as polyion (those similar to the description inInorganic Chemistry Series 7, Coordinate Stereochemistry, written byYoichi NIIMURA, published by Baihukan Co. Ltd., 65-66). In addition, thealkaline complex ion of indium and the hydrated indium ion are unstableand have low deposition potentials, but they have wide ranges of thepotential, and the hydrogen gas generation is also induced during thedeposition. Thus, when the complexing is performed with tartarate orEDTA, a stable complex ion is provided, it is possible to narrow therange of the deposition potential of indium, it is possible to separatefrom the deposition potential of hydrogen, and it is possible to depositonly indium without the accompanying generation of hydrogen.

Other than indium, tin and lead also have smaller ionization tendenciesthan zinc, so that when ions of these metals are allowed to exist in theelectrolyte solution, it is possible to deposit these metals on the zincsurface. In addition, because the collector contacts with zinc, the samepotential as that of zinc is obtained, and the above-mentioned metal isdeposited. The function for further suppression of the corrosion anddissolution by mixing the indium compound, the tin compound containingtetravalent tin, lead oxide and the like is not certain, however, thefollowing facts can be considered.

One is the fact that alloy formation may take place when these metalsare deposited on zinc and the collector. During the alloy formation,fine crystals of the deposited metal are produced, and the surfaces ofzinc and the collector are coated with homogeneous films having nodeficiency. For example, in the case of an alloy of indium-tin, finecrystals are produced when a composition near the eutectic point ofabout 50:50 in an atomic % is aimed. In the case of an alloy of thethree component system, crystals become more complicated, and coarseformation of crystal grains is prevented, so that it becomes easy toobtain a homogeneous film.

The other is the fact that characteristics possessed by each of themetals can be simultaneously utilized by mixing. Particularly in thecase of lead, if it is used alone needle-like crystals are deposited andit becomes impossible to homogeneously coat the surfaces of zinc and thecollector. However, during assembly of the battery, when the electrolytesolution containing tetravalent tin is first added and subsequently theelectrolyte solution containing lead oxide is added, the zinc and thecollector are coated with indium and tin which form relativelyhomogeneous films and then are coated with a film having needle-likecrystals of lead. The homogeneous films of indium and tin suppress thecorrosion and dissolution of zinc or the collector, and the film of leadhaving needle-like crystals strengthens the electrical contact betweenthe zinc and the collector, and enhances shock resistance and dischargecharacteristics.

In the case of a negative electrode active material such as pure zincand the like in which the hydrogen generation is large, it is difficultto form a homogeneous film due to the hydrogen generation which occursas a competitive reaction with respect to the deposition of metal on thesurface, and the effect of deposited metal becomes less. Thus, using anegative electrode active material in which zinc is added with indium,bismuth, lead, aluminum, calcium, gallium and the like, effectivelysuppresses the generation of hydrogen to some extent.

An attempt has been frequently made in which zinc is added with a metalhaving a high hydrogen overvoltage to form an alloy so as to suppresscorrosion and dissolution. It is known that the effect thereof isremarkably expresses especially when indium is added. When zinc is usedin which indium is added in a relatively high concentration, forexample, not less than 400 ppm, a part of indium and zinc is oncedissolved due to the contact with copper or the like of the collector.It is considered that the corrosion and dissolution of zinc issuppressed by a mechanism in which dissolved indium ion is deposited onthe collector, and a film of indium is formed on the collector. However,in the initial stage of the contact between zinc and the collector, theamount of indium ion to be reduced on the collector is extremely small.Thus, when one or more species of the compounds selected from the indiumcompound which is nobler than zinc, the tin compound containingtetravalent tin and lead oxide are added as the inhibitor into theelectrolyte solution or the negative electrode active material, and themetal ion is allowed to exist in the electrolyte solution in an amountsufficient to coat zinc and the collector, then it is possible toimmediately deposit lead onto zinc and the negative electrode collector,and it is possible to suppress the hydrogen generation.

When iron is abundant in zinc, there are provided many places in whichiron is exposed on the zinc surface. Zinc and iron on the surface form alocal battery in the electrolyte solution, zinc dissolves, and hydrogenis generated from iron. At the place in which hydrogen is generated, thecoating film by the inhibitor is difficult to be formed, and it isdifficult to obtain the effect of the inhibitor.

When mercuryless zinc powder in which the content of iron is not morethan 4 ppm with respect to a weight of zinc is used, one or more speciesof the compounds selected from the indium compound nobler than zinc, thetin compound containing tetravalent tin and lead oxide are added as theinhibitor into the electrolyte solution or the negative electrode activematerial, and the ion is allowed to exist in the electrolyte solution inan amount sufficient to coat zinc and the collector, then it is possibleto immediately deposit the film of metal nobler than zinc onto zinc andthe negative electrode active material, and it is possible to suppressthe corrosion and dissolution of zinc and the hydrogen generationaccompanying therewith.

It is preferable that the adding amount of the inhibitor be about10-1000 ppm with respect to the zinc powder. If the adding amount isless, it is impossible to sufficiently coat zinc and the collector, andthere is such a bad effect that needle-like crystals penetrate throughthe separator to cause a short circuit.

It is generally said that gallium, indium, lead and bismuth have highhydrogen overvoltages, and when they are added to zinc, the hydrogen gasgeneration is suppressed. It is said that aluminum and calcium smoothenthe surface during the production of zinc powder by atomization, reducethe surface area of the zinc powder, and suppress the hydrogen gasgeneration in the same manner.

In addition, although the function is not certain, the electrolytesolution is made as much as permitted by liquid leakage, thereby it ispossible to suppress the hydrogen gas generation and the self-discharge.Further, by increasing the electrolyte solution, it also becomespossible to increase the absolute amount of the inhibitor to be added inorder to suppress the hydrogen gas generation and the self-discharge,and it is considered that the inhibitor effect is also increased.

In order to allow the mercuryless battery to approximate the performanceof a battery in which mercurated zinc is contained, it is necessary thatfeatures of various techniques are understood, and that they arecombined and used. Functions of individual techniques will be shownhereinafter.

Generally speaking, the addition of metals such as indium, lead,bismuth, calcium, aluminum and the like into zinc is to prevent thecorrosion and dissolution and suppress the hydrogen gas generation.However, the role of each metal added varies. The metal having a highhydrogen overvoltage such as indium, lead and bismuth forms an alloywith zinc, increases the hydrogen overvoltage, and prevents thecorrosion and dissolution. On the other hand, calcium and aluminumsmoothen the alloy surface during manufacturing by atomization, whichlevel potential distribution, and decrease the surface area of zincparticles, so that they are effective in the prevention of the corrosionand dissolution. In addition, when hydrogen is generated on the zincsurface by the corrosion and dissolution, no inhibitor is supplied thereand no effect of the inhibitor can be also exhibited. Also in thismeaning, the alloy formation of zinc by the addition of metals accordingto the present invention is important.

The cross-linked type polyacrylic water-absorbing polymer to be used asthe gelling agent has a strong moisture holding property, which preventsthe electrolyte solution from evaporation and unnecessary movementtoward the separator and the positive electrode side. Thus, it ispossible to allow the inhibitor to be distributed all over and suppressthe increase in the internal resistance due to shortage of liquid at thelast stage of discharge.

The reason why the layer of zinc or metal having a hydrogen overvoltagehigher than that of zinc is formed at the outermost layer of thecollector is to prevent the fact that the mercuryless zinc powder as thenegative electrode active material contacts with copper of the collectorto form a battery, and hydrogen gas is also generated from it.

In addition, when the layer of zinc or metal having a hydrogenovervoltage higher than that of zinc is formed after the pressprocessing of a negative electrode casing containing the collector, itis possible to shield impurities such as iron and the like adhered tothe collector side during the processing.

Especially, it is effective to provide the alloy layer containing zincas the essential element and containing one or more species selectedfrom indium, lead and tin as the selective element on the collectorsurface. This is due to the fact that the potential of the collectorsurface becomes substantially the same as that of the mercuryless zincsurface as the negative electrode active material. Thus, even when thecollector contacts with the mercuryless zinc powder as the negativeelectrode active material, it is avoided that a local battery is formedand hydrogen gas is generated from it.

It is supposed that, even if only zinc is plated on the collector, thepotential difference may disappear and an effect may be expected,however, zinc deposited by plating or the like is extremely active andeasy to be corroded, so that little effect is provided for suppressingthe hydrogen gas formation. Thus, it is necessary to plate an alloy inwhich indium and lead are added into zinc by not less than several 10ppm. In the plating process, for the plating solution, several 10 toseveral 1000 ppm of the indium compound, lead compound and tin compoundare added into general zinc plating solutions may be needed, and for thepositive electrode, an alloy of zinc may be used. For example, indiumsulfate may be added in the case of a plating solution of the zincsulfate type, while indium cyanide may be added in the case of a platingsolution of the cyanide type.

As the inhibitor, there are the inorganic type and the organic type.Among them, the inorganic inhibitor is roughly classified into twospecies. One is a compound of metal which is nobler than zinc and has ahigher hydrogen overvoltage. For example, it is the above-mentionedindium compound such as indium sulfate, indium sulfamate, indiumchloride, indium hydroxide or the like, and they are dissolved in aconcentrated caustic alkaline solution, and form alkaline complex ioncapable of cathode reduction referred to in the plating. The alkalinecomplex ion of indium is reduced at the zinc surface representing apotential lower than the reduction potential of itself, and indium isimmediately deposited as metal. When zinc is initially coated withindium, all of the surface becomes to have the potential of indium, andthe electrochemical driving force is lost, so that further deposition ofindium is ceased. However, when the zinc surface is newly exposed bydischarge, indium which exists as the alkaline complex ion isimmediately reduced and deposited. Thus, there are provided such effectsthat the hydrogen gas generation is less even when the discharge isstopped on the way to store, and the self-discharge rate is made small.

Due to the fact that a potential lower than the reduction potential ofitself is indicated also on the collector such as copper or the likecontacting with zinc, the alkaline complex ion of indium is reduced, andindium is immediately deposited as for metal. However, the amount of theelectrolyte solution is fairly less in an actual battery, so that theinhibitor is not homogeneously distributed on the collector to provideno metal coating, and when there are bubbles between the negativeelectrode combined agent and the collector, such a place only where nometal coating is provided at all is made, and it has been impossible toexhibit a sufficient effect. Lead monoxide and the tetravalent tincompound are included in the inorganic inhibitor of this type.

The other inorganic inhibitor is oxide and hydroxide of metal baser thanzinc or non-metal. Although the function is not certain, effects areprovided in the suppression of the hydrogen gas generation and theimprovement in electric characteristics, and as the representative one,there is barium hydroxide or the like which is hydroxide of alkalineearth metal. However, when a collector which having no layer of zinc ormetal having a hydrogen overvoltage higher than that of zinc for theoutermost layer is used, the hydrogen gas generation due to the contactbetween the collector and zinc is too large, and little effect thereofis expressed.

The surfactant of organic type suppresses the corrosion and dissolutionof zinc because the hydrophilic group adheres to the zinc surface andthe hydrophobic group suppresses the approach of water and hydroxylgroup to the surface. The effect is similar to that of a hydroxide ofalkaline metal, and it is desirable to combine and use with thecollector having the layer of zinc or metal having a hydrogenovervoltage higher than that of zinc for the outermost layer.

In addition, although the function is not certain, when polypxyethylenealkylamide, barium hydroxide and the like are combined and used, aremarkable hydrogen gas generation suppressing effect is obtained.However, organic surfactants have a possibility to be excessivelyadhered onto the surfaces of zinc and the collector and inhibit thereduction on the surface in the combination with the indium compound orlead monoxide, so that it is desirable that the adding amount is made assmall as possible within a range which can provide the effect.

It has been found out that there are roles of each one such that thecoating of zinc or metal having a hydrogen overvoltage higher than thatof zinc onto the collector suppresses the hydrogen gas generation due tothe contact between zinc and the collector, the indium compound and leadmonoxide suppress the self-discharge after partial discharge, and thealkaline earth hydroxide improves electric characteristics, and themaximum effect is obtained when they are combined and used. Namely, whenthe alkaline battery is manufactured by using the collector having thelayer of zinc or metal having a hydrogen overvoltage higher than that ofzinc for the outermost layer, it is possible to obtain the one in whichthe self-discharge rate is small before use and after partial discharge,and the electric characteristic is good.

When the collector is coated with a zinc alloy, the zinc.alloy becomesthe negative electrode active material as it is, so that by thickeningthe zinc alloy layer on the collector surface, it is possible to make upa battery capacity reduced by elimination of mercury. For example, whena collector having a diameter of 6 mm is plated by 10 Am, the amount ofthe negative electrode active material increases by 2 mg because thespecific gravity of zinc is 7.13. Provided that the amount of thenegative electrode active material as zinc powder is 30 mg, it ispossible to increase the capacity by about 6.7% without changing thespace in the battery can so much. However, as compared with the powderynegative electrode active material, the surface area is small, so thatno large current can be expected. However, it is most suitable forincreasing the capacity of a batteries which perform minute dischargesuch as batteries for clocks and watches.

In addition, to thicken the zinc alloy plating is advantageous also inthe processing of battery cans. Generally, the negative electrode canhaving the negative electrode collector is manufactured by punching ahoop material in many cases. In this case, if the zinc alloy has platedrather thickly beforehand at the side of hoop material for serving asthe collector, the probability to expose metal such as for examplecopper as a base substrate during processing is reduced.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 shows the generated amount of hydrogen gas with respect to dayspassed.

FIG. 2 shows the hydrogen gas generated amount with respect to theindium sulfate concentration.

FIG. 3 shows current-potential curves at ordinary temperature in thepotassium hydroxide solution.

FIG. 4 shows current-potential curves at ordinary temperature in thepotassium hydroxide solution in which zinc oxide is dissolved up toapproximate saturation.

FIG. 5 shows the hydrogen gas generation amount with respect to dayspassed.

FIG. 6 shows the hydrogen gas generation amount with respect to theindium sulfate concentration.

FIG. 7 is a figure showing the generation amount of hydrogen gas withrespect to the amount of lead monoxide added into the electrolytesolution of the present invention.

FIG. 8 is a figure showing the generation amount of hydrogen gas withrespect to the amount of lead monoxide added into the electrolytesolution.

FIG. 9 shows the hydrogen generation amount with respect to the amountof water added per 1 mg of zinc when the electrolyte solution of thepotassium hydroxide type is used.

FIG. 10 shows the hydrogen generation amount with respect to the amountof water added per 1 mg of zinc when the electrolyte solution of thesodium hydroxide type is used.

FIG. 11 shows the generation amount of hydrogen gas with respect to dayspassed when the inhibitor of the present invention is added to theplated copper plate.

FIG. 12 shows the generation amount of hydrogen gas with respect to dayspassed when the inhibitor of the present invention is added to thenon-plated copper plate.

FIG. 13 shows the change in the self-discharge rate with respect to theinhibitor concentration.

FIG. 14 shows the change in the self-discharge rate after 50% depthdischarge with respect to the inhibitor concentration.

FIG. 15 shows the generation amount of hydrogen gas with respect to dayspassed when the inhibitor of the present invention is added to theplated copper plate.

FIG. 16 shows the generation amount of hydrogen gas with respect to dayspassed when the inhibitor of the present invention is added to thenon-plated copper plate.

FIG. 17 shows the change in the self-discharge rate with respect to theinhibitor concentration.

FIG. 18 shows the change in the self-discharge rate after 50% depthdischarge with respect to the inhibitor concentration.

FIG. 19 is a figure showing the hydrogen gas generation amount withrespect to barium hydroxide.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

The present invention will be explained hereinafter in accordance withEmbodiments.

The effect of the case in which the indium compound of the presentinvention is used will be explained in accordance with the Embodiments1-3, and the Comparative example 1.

Embodiment 1

Into a specially prepared test tube having a volume of 25 ml andgraduated to know the gas generation amount were added beforehand 2 g ofzinc powder containing 500 ppm of each of bismuth, indium and leadmanufactured by the atomization method, and a copper piece as the samematerial as a collector having an area of 0.6 cm² and a thickness of 0.1mm, an electrolyte solution to be tested was added thereto to heat to60° C., and the volume of generated hydrogen gas was measured for 7days. The number of test repeating was made to 10 times, and an averagevalue thereof was used as a result. The electrolyte solution wasprepared such that by making, a solution in which potassium hydroxidewas 30% by weight and zinc oxide was added up to approximate saturationin the case of the potassium hydroxide type, or a solution in whichsodium hydroxide was 25% by weight and zinc oxide was added up toapproximate saturation in the case of the sodium hydroxide type, as abase, an indium compound was added thereto.

Indium sulfate made by Nihon Kagaku Sangyo Co., Ltd., indium sulfamate35% solution also made by Nihon Kagaku Sangyo Co., Ltd., indium chloridemade by Wako Pure Chemical Industries., Ltd., and indium cyanide made byIto Phamaceutical Co., Ltd. were used. The adding amount of the indiumcompound was 1000 ppm with respect to the electrolyte solution. Resultsare shown in the hydrogen generation amount in Table 1. The unit isμL/g/day.

Comparative example 1

With the same test as in Embodiment 1, the measurements were performedfor one in which no indium compound of the present invention was added,and one in which indium oxide was added by 1000 ppm with respect to theelectrolyte solution. Indium oxide made by Kanto Chemical Co., Ltd. wasused. Results are shown in the hydrogen generation amount in Table 1 inthe same manner. The unit is μL/g/day.

TABLE 1 Hydrogen evolution volume and comparison of discharge capacityof experimental cell Hydrogen evolution Comparison Indium compoundvolume of discharge Electrolyte 1000 ppm μL/g/day capacity Examples ofthe invention 1 KOH InSO₄ 24.29 102 Indium sulfate 2 KOH In(NH₂SO₃)₃30.51 102 Indium Sulfamate 3 KOH Indium chloride 35.40 101 4 KOH Indiumcyanide 20.66 103 5 NaOH InSO₄ 18.11 102 Indium sulfate 6 NaOHIn(NH₂SO₃)₃ 27.43 102 Indium Sulfamate 7 NaOH Indium chloride 29.67 1028 NaOH Indium cyanide 14.21 103 Examples for comparison 9 KOH — 516.63100 10 KOH Indium oxide 196.10 97 11 NaOH — 420.36 100 12 NaOH Indiumoxide 150.88 97

In FIG. 1, the hydrogen gas generation amount with respect to the numberof test days of the samples using the electrolyte solution of thepotassium hydroxide series, is shown. It has been found that in the caseof no addition of the indium compound shown in 1 in the figure, thehydrogen generation amount increases exponentially with respect to thenumber of test days. It is understood that in the case of addition ofthe indium sulfate in 2 in the figure which is the indium compound ofthe present invention, the generation of hydrogen gas is suppressed. Inthe case of addition of the indium oxide in 3 in the figure, thehydrogen gas generation in the former half is high. This is consideredto be due to the fact that the solubility of indium oxide is bad, thesupply of indium ion to the electrolyte solution is not sufficient, anda long time is required to coat the surfaces of zinc and copper.

In addition, it is considered that the reason why a bad result is givenin the former half as compared with no addition is that indium oxidealso contacts with zinc and the collector, and a local battery isformed. Indium cyanide presented a good result from a viewpoint ofcharacteristics, however, it is desirable not to use it because there isthe possibility of occurrence of a new environmental pollution problem.

Embodiment 2

Into a positive electrode can were added a part of an electrolytesolution and 116 mg of a pellet (silver oxide content of 98%) which wasmolded by adding a combined agent into silver oxide, and a separator ofpolyethylene and a separator of cellophane were set in place. Next, agasket of nylon was pushed and fitted into the positive electrode can,an impregnating agent, a gelling agent, 30 mg of zinc powder, aninhibitor and the like were added, the remainder of the electrolytesolution was added dropwise, and then a negative electrode can was setin place to seal the battery and then 100 pieces for every kind ofbutton type silver oxide batteries were manufactured. The same zinc asin Embodiment 1 and the electrolyte solution in Table 1 were used, andthe battery size was that of the SR621 type.

However, the added amount of indium was 1000 ppm with respect to theamount of zinc. Results are shown in the discharge index in Table 1.Discharge characteristics were measured using a resistance of 200 Ω bymeans of the direct current method, when the electrolyte solution was ofthe potassium hydroxide series, or the pulse method, when theelectrolyte solution was of the sodium hydroxide series. In any case, noaddition of the inhibitor was regarded to have a discharge index of 100.As understood also from the results, it has been found that the indiumcompound of the present invention is effective also in the dischargecharacteristics.

Embodiment 3

Using a gasket of polypropylene specially prepared for allowing hydrogento penetrate in the same manner as described for Embodiment 2, a buttontype silver oxide battery was manufactured. Ten pieces of themanufactured silver oxide batteries were put into a vessel made of glassfilled with liquid paraffin in a high temperature tank, a collectingtube having graduations at an upper portion was attached, and the amountof generated hydrogen gas was measured. This state was maintained at 60°C. for 20 days which corresponds to a term of about 1 year, and thehydrogen gas generation amount after 20 days was investigated. Withrespect to the inhibitor, the test was performed using indium sulfate ata concentration of 10 ppm to 5% with respect to the weight of zinc.Evaluation results are shown in FIG. 2. According to the figure, it isunderstood that the inhibitor effectively works at 100 ppm to 1%.

The gasket of polypropylene was returned to one made of nylon, and abutton type silver oxide battery was manufactured in a range of anindium sulfate concentration of 100 ppm to 1% in which the gasgeneration was less. Ten pieces of the manufactured batteries were putinto a vessel made of glass filled with liquid paraffin in a hightemperature tank maintained at 25° C. in the same manner, and acollecting tube for generating hydrogen gas was attached to the upperportion. Hydrogen gas generation, expansion of the can and liquidleakage were not observed after 20 days at 60° C. For indium sulfate, itwas effective in the concentration of 100 ppm to 1% with respect tozinc, however, the same effect was observed also in the case of otherindium compounds by adjusting the mole number and determining theconcentration range.

In the actual trial production of batteries, there is given a valuesmaller than the hydrogen gas generation amount in the experiment inEmbodiment 1. In respect to this fact, it is considered that the copperpiece used in Embodiment 1 is different from a structure of an actualcollector, and a part of generated hydrogen gas has been consumed by thereduction of silver oxide and the like. The method in Embodiment 1 isdifferent in the amount order of hydrogen gas generation, but it issufficient as a method for observing substituted characteristics forpredicting hydrogen generation in an actual battery.

In accordance with Embodiments 4-7, the effect of the case in which theindium compound and the complexing agent of the present invention areused will be explained.

Embodiment 4

For an electrolyte solution of 30% by weight of potassium hydroxide,using a platinum electrode of 1 cm² as the working electrode, a platinumelectrode of 1 cm² as the counter electrode in the same manner, and acomparative electrode HC-205C made by Toa Electronics Ltd. as thereference electrode, the current-potential curve during deposition ofindium was determined. The potential was scanned from the plus side tothe minus side at a speed of 100 mV/second. The current for eachpotential represents the reaction at the electrode and, for example, ifthe reduction reaction such as deposition of indium and generation ofhydrogen gas occurs, a current caused thereby flows.

Results are shown in FIG. 3. 4 in the figure is a case where indiumsulfamate was added to the electrolyte solution by 0.1 mol/L, in thiscase, the current began to flow from the vicinity of −1.1 V with respectto the reference electrode, and indium was deposited accompanyinghydrogen generation. 5 is a current-potential curve of a case in which0.1 mol/L of potassium tartarate was added to the electrolyte solution,and then 0.1 mol/L of indium sulfamate was added. It was found thatindium was deposited at the vicinity of −1.4 V, and hydrogen wasgenerated under the vicinity of −2.0 V. This is considered such thatsince indium having a high hydrogen overvoltage was deposited on theelectrode surface, the potential for hydrogen generation was shiftedtoward the minus side.

Thereby, the potential of deposition of indium could be separated fromthat of hydrogen generation. It is considered that also in the case ofan actual battery, if indium is deposited previously, the hydrogen gasgeneration further becomes smaller. In the case where indium sulfamateand potassium tartarate are added to the electrolyte solution, whenindium sulfamate is added previously, indium hydroxide and polyion aregenerated to become cloudy, while when potassium tartarate is addedpreviously, no turbidity occurs.

In 6 in FIG. 3 is shown a current-potential curve of a case where indiumsulfamate was added to the electrolyte solution by 0.1 mol/L, and then0.1 mol/L of potassium tartarate was added. A small peak probablyconsidered as indium is observed in the vicinity of −1.4 V in thefigure, however, indium is deposited accompanying hydrogen generationfrom the vicinity of −1.1 V with respect to the reference electrode inthe same manner as the case of no addition of potassium tartarate, andthe effect of addition of the complexing agent becomes small. This alsocan be said for other indium compounds and complexing agents, and inorder to immediately form the complex ion of indium and preventprecipitation, it is necessary to dissolve the complexing agentpreviously in the electrolyte solution.

Embodiment 5

For an electrolyte solution of 30% by weight of potassium hydroxide inwhich zinc oxide was added up to approximate saturation, using aplatinum electrode of 1 cm² as the working electrode, a platinumelectrode of 1 cm² as the counter electrode in the same manner, and acomparative electrode HC-205C made by Toa Electronics Ltd. as thereference electrode, the current-potential curve during deposition ofindium was determined. Results are shown in FIG. 7 in the figure is acase where indium sulfamate was added to the electrolyte solution by 0.1mol/L, and metal was deposited accompanying hydrogen generation from thevicinity of −1.56 V with respect to the reference electrode. Thedeposition potential of metal is lower than that of a case of noaddition of zinc oxide, so that there is a possibility that it is analloy of zinc and indium.

8 is a current-potential curve of a case where 0.1 mol/L of potassiumtartarate was added to the electrolyte solution, and then 0.1 mol/L ofindium sulfamate was added. There is a peak considered as the depositionof indium at the vicinity of −1.5 V, and then metal was depositedaccompanying hydrogen generation from the vicinity of −1.56 V. In orderto confirm the deposited substance at the vicinity of −1.5 V, thepotential was held at −1.5 V for 30 seconds, and the deposited metal wasimmersed in nitric acid. If it was zinc, it might be instantlydissolved, but it was difficult to dissolve, so that the depositedsubstance is postulated to be indium or an alloy having a large amountof indium.

As a result of the measurement, the electrode potential of zinc was−1.509 V with respect to the reference electrode. It just corresponds toa potential at which only indium or an alloy having a large amount ofindium is deposited in a solution containing a complexing agent. Namely,indium or the alloy having a large amount of indium is deposited on zincand the collector contacting with zinc, which prevents zinc and thecollector from corrosion and dissolution.

Embodiment 6

Into a specially prepared test tube having a volume of 25 ml andgraduated to determine the gas generation amount, there was added 2 g ofzinc powder containing 500 ppm of each of bismuth, indium and leadmanufactured by the atomization method, and a copper piece having thesame material as the collector having an area of 0.6 cm² and a thicknessof 0.1 mm, an electrolyte solution to be tested was then added theretoto heat to 60° C., and the volume of generated hydrogen gas was measuredfor 7 days. The number of repetitions of the test was 10, and an averagevalue thereof was used as a result.

The electrolyte solution was prepared by preparing a solution in whichpotassium hydroxide was 30% by weight and zinc oxide was added up toapproximate saturation in the case of the potassium hydroxide series, ora solution in which sodium hydroxide was 25k by weight and zinc oxidewas added up to approximate saturation in the case of the sodiumhydroxide series, as a base, and a complexing agent and an indiumcompound were added thereto.

Indium sulfate made by Nihon Kagaku Sangyo Co., Ltd., indium sulfatnate35% solution also made by Nihon Kagaku Sangyo Co., Ltd., indium chloridemade by Wako Pure Chemical Industries., Ltd., and indium cyanide made byIto Phamaceutical Co., Ltd. were used.

The adding amount of the indium compound was 1000 ppm with respect tothe electrolyte solution, and the adding amount of the complexing agentwas made 2-fold excessive in a mole ratio of indium ion.

Results in the case where the indium compound was added without addingof the complexing agent are shown in Table 2. The hydrogen gasgeneration amount is shown in Table 3 in the case where the complexingagent was added. The hydrogen generation index is the value in which thehydrogen generation amount in the test using the same electrolytesolution except for the complexing agent is regarded as 100.

When the hydrogen gas generation amount is observed, so as postulatedfrom the current-potential curve, it is understood that the hydrogengeneration is suppressed. Although the effect is observed also in thecyanide series, however, the cyanide type has a possibility to lead to anew environmental pollution problem, so that it is not desirable to useit.

TABLE 2 Hydrogen evolution volume without complexinq agent andcomparison of discharge capacity of experimental cell Hydrogen Examplesevolution Comparison of the Indium compound Complexing volume ofdischarge invention Electrolyte 1000 ppm agent μL/g/day capacity 1 KOHIndium sulfate — 24.29 100 2 KOH Indium sulfamate — 30.51 100 3 KOHIndium chloride — 35.40 100 4 KOH Indium cyanide — 20.66 100 5 NaOHIndium sulfate — 18.11 100 6 NaOH Indium sulfamate — 27.43 100 7 NaOHIndium chloride — 29.67 100 8 NaOH Indium cyanide — 14.21 100

TABLE 3 Comparison of hydrogen evolution volume with complexing agentand comparison of discharge capacity of experimental cell HydrogenExamples evolution Comparison of the Indium compound Complexing volumeof discharge invention Electrolyte 1000 ppm agent μL/g/day capacity 9KOH Indium sulfate Potassium tartrate 98 102 10 KOH Indium sulfamatePotassium tartrate 99 1o1 11 KOH Indium chloride Potassium tartrate 98103 12 KOH Indium cyanide Potassium tartrate 99 102 13 NaOH Indiumsulfate Sodium tartrate 98 102 14 NaOH Indium sulfamate Sodium tartrate97 103 15 NaOH Indium chloride Sodium tartrate 98 101 16 NaOH Indiumcyanide Sodium tartrate 98 102 17 KOH Indium sulfate EDTA 98 102 18 KOHIndium sulfamate EDTA 98 102 19 KOH Indium chloride EDTA 99 103 20 KOHIndium cyanide EDTA 98 103 21 NaOH Indium sulfate EDTA 97 101 22 NaOHIndium sulfamate EDTA 99 102 23 NaOH Indium chloride EDTA 98 102 24 NaOHIndium cyanide EDTA 97 102 25 KOH Indium sulfate Glycine 99 101 26 KOHIndium sulfamate Glycine 99 100 27 KOH Indium chloride Glycine 99 101 28KOH Indium cyanide Glycine 99 101 29 NaOH Indium sulfate Glycine 99 10130 NaOH Indium sulfamate Glycine 99 100 31 NaOH Indium chloride Glycine99 101 32 NaOH Indium cyanide Glycine 98 101 33 KOH Indium sulfatePotassium cyanide 97 103 34 KOH Indium sulfamate Potassium cyanide 97103 35 KOH Indium chloride Potassium cyanide 97 103 36 KOH Indiumcyanide Potassium cyanide 97 104 37 NaOH Indium sulfate Sodium cyanide97 103 38 NaOH Indium sulfamate Sodium cyanide 97 102 39 NaOH Indiumchloride Sodium cyanide 97 102 40 NaOH Indium cyanide Sodium cyanide 96103

Embodiment 7

Into a positive electrode can there were added part of an electrolytesolution and 116 mg of a pellet (silver oxide content of 98%) which wasmolded by putting a combined agent into silver oxide, and a separator ofpolyethylene and a separator of cellophane were set in place. Next, agasket of nylon was pushed and fitted into the positive electrode can,an impregnating agent, a gelling agent, 30 mg of zinc powder, aninhibitor and the like were added, the remainder of the electrolytesolution was added dropwise, and then a negative electrode can was setin place to seal the battery and 100 pieces were manufactured for everykind of button type silver oxide batteries. The same zinc as inEmbodiment 6 and the electrolyte solution in Table 2 were used, and thebattery size selected was as that of the SR621 type.

However, the amount of indium added was 1000 ppm with respect to theamount of zinc, and the amount of the complexing agent added was 2-foldin a mole ratio of indium ion. Discharge characteristics were measuredusing a resistance of 200 Ω by means of the direct current method whenthe electrolyte solution was the potassium hydroxide series or the pulsemethod when it was the sodium hydroxide series. In any case, no additionof the complexing agent was regarded to have a discharge index of 100.Results are shown with the right discharge index in Table 2. The effectof glycine is rather small, however, the effect was observed for all ofthe tested complexing agents.

The foregoing description has been made on the basis of an embodimentfor the representative indium compound and the complexing agent asdescribed above, however, the effects of the indium compound and thecomplexing agent can be easily postulated if the current-potential curveis determined in the same manner as shown in embodiments 4 and 5. It isunderstood that other indium compounds and complexing agents exhibitingthe same effects can be applied to the present invention. In addition,an example for the silver battery has been described in Embodiment 4,however, the same effect can be expected even in the case of alkalinemanganese batteries using zinc, air batteries and the like.

In addition, in the case of a negative electrode active material such aspure zinc and the like in which hydrogen generation is large, ahomogeneous film is difficult to be formed due to hydrogen generationwhich occurs on the surface as a competitive reaction against indiumdeposition, and the effect of indium deposition becomes small. Thus, itis effective to use a negative electrode active material in which thehydrogen generation is suppressed to some extent by adding indium,bismuth, lead, aluminum, gallium, calcium and the like into zinc.

In Embodiment 8-11, the case in which two or more species selected fromthe group consisting of the indium compound, the tin compound containingtetravalent tin and lead oxide are used as the inhibitor of the presentinvention will be explained.

Embodiment 8

Into a specially prepared test tube having a volume of 25 ml graduatedto measure the amount of gas generated, there were added 2 g of zincpowder containing 500 ppm of each of bismuth, indium and leadmanufactured by the atomization method, and a copper piece as the samematerial as a collector having an area of 0.6 cm² and a thickness of 0.1mm, an electrolyte solution to be tested was added thereto to heat to60° C., and the volume of generated hydrogen gas was measured for 7days.

The number of test repetitions was 10, and the average value thereof wasused as a result. The electrolyte solution was prepared such that byadding as a base a solution in which potassium hydroxide was 30% byweight and zinc oxide was added up to approximate saturation in the caseof the potassium hydroxide series, or a solution in which sodiumhydroxide was 25% by weight and zinc oxide was added up to approximatesaturation in the case of the sodium hydroxide series, and compoundselected from indium sulfate, indium sulfamate, sodium stannate and leadoxide were added thereto.

Indium sulfate and sodium stannate made by Nihon Kagaku Sangyo Co.,Ltd., indium sulfamate 35% solution also made by Nihon Kagaku SangyoCo., Ltd., and lead oxide made by Wako Pure Chemical, Ltd. were used.The added amount of the compounds was 1000 ppm in total with respect tothe electrolyte solution. The results of the amounts of hydrogengenerated are shown in Table 4.

TABLE 4 Hydrogen evolution volume and comparison of discharge capacityof experimental cell The number of copper Comparison Examples Amount ofadded compound pieces: Hydrogen of of the Indium Indium Lead SodiumElectro- soaked in evolution discharge invention sulfate sulfamate oxidestannate lyte electrolyte μ/g/day capacity 1 1000 KOH 0 37.86 — 2 1000KOH 0 27.14 — 3 1000 KOH 0 157.36 — 4 1000 KOH 0 26.81 — 5 1000 KOH 524.29 102 6 1000 KOH 5 30.51 102 7 1000 KOH 5 55.56 103 8 1000 KOH 539.15 101 9 500 500 KOH 5 21.43 103 10 500 500 KOH 5 35.71 102 11 500500 KOH 5 50.00 103 12 500 500 KOH 5 18.57 103 13 500 500 KOH 5 46.43102 14 333 333 333 KOH 5 42.86 103 15 333 333 333 KOH 5 42.86 103 161000 NaOH 0 35.26 — 17 1000 NaOH 0 23.85 — 18 1000 NaOH 0 103.45 — 191000 NaOH 0 24.17 — 20 1000 NaOH 5 22.14 102 21 1000 NaOH 5 27.51 102 221000 NaOH 5 48.23 103 23 1000 NaOH 5 35.12 101 24 500 500 NaOH 5 18.82103 25 500 500 NaOH 5 31.48 102 26 500 500 NaOH 5 44.22 103 27 500 500NaOH 5 16.11 103 28 500 500 NaOH 5 39.64 102 29 333 333 333 NaOH 5 37.26103 30 333 333 333 NaOH 5 35.12 103 31 KOH 5 516.63 100

For comparison, experiment results without addition of the copper platein the same experiment as Embodiment 8 are shown in examples 1-4 and16-19 of Table 4. In addition, a result of no addition of the compoundis shown in example 31 of Table 4. The amount of hydrogen gas generatedwith respect to the number of test days for example 31 in Table 4 andexample 12 in Table 4 as a combination of indium sulfamate and leadoxide whose gas generation was small is shown in FIG. 5. It isunderstood that in the case of no addition of the compound, the amountof hydrogen generated increases with respect to the number of test daysexponentially, and it is understood that in the case of the addition ofindium sulfamate and lead oxide, the generation of hydrogen gas issuppressed.

As seen from the data of examples 3 and 4 in Table 4, lead oxideprovides a relatively large amount of hydrogen generation. This isconsidered to be due to the fact that when lead is deposited,needle-like crystals are generated, making it impossible tohomogeneously coat the surfaces of zinc and the collector. From aviewpoint of the combination, it is understood that the combination ofthe compound of indium and lead oxide is especially good, suppressinghydrogen generation and improving the discharge characteristics.

Embodiment 9

Into a positive electrode can were added a part of an electrolytesolution and 116 mg of a pellet (silver oxide content of 98%) which wasmolded by adding a combined agent into silver oxide. A separator ofpolyethylene and a separator of cellophane were then set in place. Next,a gasket of nylon was pushed and fitted into the positive electrode can,an impregnating agent, a gelling agent, and 30 mg of zinc powder wereadded, in the remainder of the electrolyte solution a compound selectedfrom the group consisting of indium sulfate, indium sulfamate, sodiumstannate and lead oxide was added dropwise, and then a negativeelectrode can was set in place to seal the battery and 100 pieces weremanufactured for every kind of button type silver oxide batteries.

The same zinc as in embodiment 8 and the electrolyte solutioncomposition in Table 4 were used, and the battery size selected was asthat of the SR621 type. However, the added amount of the compound was1000 ppm with respect to the zinc amount. Results are shown in thedischarge index in Table 4. Discharge characteristics were measuredusing a resistance of 200 Ω by means of the direct current method whenthe electrolyte solution was the potassium hydroxide series or the pulsemethod when the electrolyte solution was the sodium hydroxide series. Inany case, no addition of the inhibitor was regarded to have a dischargeindex of 100. As understood also from the results, it has been foundthat the present invention is effective also in the dischargecharacteristics.

Especially, when lead oxide is added to the electrolyte solution thedischarge index is superior over conventional methods in that there isan improvement in the electric contact by needle-like crystals. From aviewpoint of the combination, it is understood that the combination ofthe compound of indium and lead oxide is especially good, suppressinghydrogen generation and improving the discharge characteristics. It willbe appreciated that indium suppresses the gas generation from zinc andthe collector, and that lead oxide improves the dischargecharacteristics.

Embodiment 10

Using a gasket of polypropylene specially prepared for allowing hydrogento penetrate in the same manner as Embodiment 9, a button type silveroxide battery was manufactured. Ten pieces of the manufactured silveroxide batteries were placed into a vessel made of glass filled withliquid paraffin in a high temperature tank, a collecting tube havinggraduations at an upper portion was attached, and the amount ofgenerated hydrogen gas was measured. In this state, the battery wasmaintained at 60° C. for 20 days, which is so as said to correspond to aterm of about 1 year, and the hydrogen gas generation amount after 20days was investigated. With respect to the added compound, the test wasperformed using indium sulfate and lead oxide in a weight ratio of 1:1at a concentration of 10 ppm to 5% in total with respect to the weightof zinc. Evaluation results are shown in FIG. 6. According to thefigure, it is understood that the added compound effectively works at 50ppm to 1%.

The gasket of polypropylene was returned to one made of nylon, and abutton type silver oxide battery was manufactured in a range ofconcentration of 50 ppm to 1% using indium sulfate and lead oxide inwhich the gas generation was less. Ten pieces of the manufacturedbatteries were put in a vessel made of glass filled with liquid paraffinin a high temperature tank maintained at 60° C. in the same manner, anda collecting tube for generating hydrogen gas was attached to the upperportion. Hydrogen gas generation, expansion of the can and liquidleakage were not observed after 20 days at 60° C.

Indium sulfate and lead oxide were effective for zinc at theconcentration of 50 ppm to 1%, however, the same effect was observedalso in the case of other combinations of compounds by adjusting themole number and determining the concentration range.

In the actual trial production of batteries, a hydrogen gas generationvalue smaller than the hydrogen gas generation amount in the experimentin Embodiment 8 was observed. That is, it is considered that the copperpiece used in Embodiment 8 is different from the structure of an actualcollector, a part of generated hydrogen gas having been consumed by thereduction of silver oxide, and the like. The method in Embodiment 8 isdifferent in the amount order of hydrogen gas generation, but it issufficient as a method for observing substituted characteristics forpredicting hydrogen generation in an actual battery.

Embodiment 11

Using a gasket of polypropylene specially prepared for allowing hydrogento penetrate in the same manner as Embodiment 9, a button type silveroxide battery was manufactured. However, two kinds of electrolytesolutions, one of indium sulfate and another of lead oxide of 50 ppmwith respect to zinc, were prepared and they were added by dividing intotwo times with changing the order. With respect to the manufacturedbutton type silver oxide batteries, the test was performed at 60° C. for20 days in the same manner as Embodiment 9. The hydrogen generationamount was 0.10 μL/g/day for one in which indium sulfate was added, andit was 0.15 μL/g/day for one in which lead oxide was added. Asunderstood from the results, an electrolyte solution in which indiumsulfate was added has a larger effect for the hydrogen gas generation.

In accordance with Embodiments 12-14, the effect of the case where zinccontaining indium is used with one or more species of compounds selectedfrom the indium compound, a compound containing tetravalent tin and leadoxide as the inhibitor of the present invention will be explained.

Embodiment 12

Into a specially prepared test tube having a volume of 25 ml graduatedto indicate the amount of gas generation, 2 g of zinc powder containingindium manufactured by the atomization method and a copper piece of thesame material as a collector having an area of 0.6 cm² and a thicknessof 0.1 mm were added, an electrolyte solution to be tested was thenadded thereto and heated to 60° C., and the volume of generated hydrogengas was measured for 7 days. The number of repetition of the test was10, and an average value thereof was used as a result. The electrolytesolution was prepared by making a solution in which potassium hydroxidewas 30% by weight and zinc oxide were added up to approximate saturationin the case of the potassium hydroxide series, or a solution in whichsodium hydroxide was 25% by weight and zinc oxide were added up toapproximate saturation in the case of the sodium hydroxide series as abase, and an inhibitor according to the present invention, such as leadmonoxide and the like, was added thereto.

In Table 5, the adding amount of indium into the zinc powder and thegeneration amount of hydrogen gas with respect to the adding amount oflead monoxide are shown. The adding amount of lead monoxide is shown byppm with respect to the electrolyte solution. Results are also shown inthe hydrogen generation amount in Table 5.

TABLE 5 Hydrogen volume generated from zinc powder ConcentrationHydrogen Indium content of PbO in evolution Experimental Electro- ofzinc powder electrolyte volume No. lyte ppm ppm μL/g/day 1 KOH 200 0603.31 2 KOH 200 10 398.88 3 KOH 200 50 102.56 4 KOH 200 100 14.29 5 KOH200 500 87.01 6 KOH 200 1000 105.70 7 KOH 200 5000 122.43 8 KOH 500 0516.92 9 KOH 500 10 30.01 10 KOH 500 50 20.13 11 KOH 500 100 6.21 12 KOH500 500 14.73 13 KOH 500 1000 40.56 14 KOH 500 5000 143.32 15 KOH 1800 099.21 16 KOH 1800 10 10.05 17 KOH 1800 50 5.33 18 KOH 1800 100 5.05 19KOH 1800 500 10.11 20 KOH 1800 1000 31.01 21 KOH 1800 5000 142.58 22NaOH 200 0 55.01 23 NaOH 200 10 327.38 24 NaOH 200 50 70.25 25 NaOH 200100 10.67 26 NaOH 200 500 62.98 27 NaOH 200 1000 85.22 28 NaOH 200 5000110.12 29 NaOH 500 0 501.39 30 NaOH 500 10 25.52 31 NaOH 500 50 16.33 32NaOH 500 100 3.99 33 NaOH 500 500 9.63 34 NaOH 500 1000 25.42 35 NaOH500 5000 103.44 36 NaOH 1800 0 82.54 37 NaOH 1800 10 10.11 38 NaOH 180050 4.87 39 NaOH 1800 100 4.51 40 NaOH 1800 500 8.73 41 NaOH 1800 100024.42 42 NaOH 1800 5000 121.12

The hydrogen gas generation results in the electrolyte solution of thepotassium hydroxide series are shown in FIG. 7. 1 in the figure is acase where zinc powder added with 200 ppm of indium was used, and thereis an effect of suppressing hydrogen generation at an adding amount oflead monoxide of about 100-400 ppm. 2 is a case where zinc powder addedwith 500 ppm of indium was used, and there is an effect of suppressinghydrogen generation at an adding amount of lead monoxide of not lessthan 10 ppm. 3 is a case where zinc powder added with 1800 ppm of indiumwas used, and there is an effect in a concentration range equivalent tothat in 2. Especially when indium is added in a high concentration insuch a manner, the effect at an adding amount of lead monoxide of notmore than 100 ppm is remarkable, and it is possible to reduce the addedamount of lead to reduce environmental pollution.

Embodiment 13

Into a positive electrode can there were added a part of an electrolytesolution and 116 mg of a pellet (silver oxide content of 98%) which wasmolded by adding a combined agent into silver oxide, and a separator ofpolyethylene and a separator of cellophane were set in place. Next, agasket of nylon was pushed and fitted into the positive electrode can,an impregnating agent, a yelling agent, 30 mg of zinc powder, aninhibitor and the like were added, the remainder of the electrolytesolution was added dropwise, and then a negative electrode can was setin place to seal the battery and 100 pieces for every kind of buttontype silver oxide batteries were manufactured. The battery size was madeas that of an SR621 type. The electrolyte solution was made again so asto allow the added amount of lead monoxide to be an amount with respectto the zinc amount. They were stored at 60° C. for 20 days, and resultsof measurement of the self-discharge rate are shown in Table 6.

TABLE 6 Self-discharge rate of cell and hydrogen evolution rate Amountof Indium PbO added to content electrolyte Self- Hydrogen of zinc (PbOweight to discharge evolution Experimental Electro- powder zinc weight)rate rate No. lyte ppm ppm % μL/g/day 1 KOH 200 0 12.1 1.23 2 KOH 200 109.9 0.95 3 KOH 200 50 7.4 0.88 4 KOH 200 100 4.1 0.50 5 KOH 200 500 8.70.71 6 KOH 200 1000 9.1 0.91 7 KOH 200 5000 15.8 1.56 8 KOH 500 0 11.21.11 9 KOH 500 10 4.2 0.56 10 KOH 500 50 3.5 0.41 11 KOH 500 100 2.50.35 12 KOH 500 500 2.9 0.32 13 KOH 500 1000 3.6 0.47 14 KOH 500 500018.9 1.49 15 KOH 1800 0 10.3 1.02 16 KOH 1800 10 2.2 0.30 17 KOH 1800 501.7 0.25 18 KOH 1800 100 1.5 0.22 19 KOH 1800 500 2.1 0.28 20 KOH 18001000 3.7 0.39 21 KOH 1800 5000 16.6 1.70 22 NaOH 200 0 10.3 1.15 23 NaOH200 10 8.2 0.90 24 NaOH 200 50 6.5 0.74 25 NaOH 200 100 3.3 0.42 26 NaOH200 500 7.5 0.72 27 NaOH 200 1000 8.1 0.86 28 NaOH 200 5000 13.2 1.35 29NaOH 500 0 10.2 1.00 30 NaOH 500 10 4.0 0.44 31 NaOH 500 50 2.9 0.32 32NaOH 500 100 2.2 0.30 33 NaOH 500 500 2.3 0.29 34 NaOH 500 1000 3.1 0.4835 NaOH 500 5000 16.7 1.38 36 NaOH 1800 0 8.9 0.90 37 NaOH 1800 10 1.90.31 38 NaOH 1800 50 1.3 0.21 39 NaOH 1800 100 0.9 0.19 40 NaOH 1800 5001.5 0.25 41 NaOH 1800 1000 2.9 0.33 42 NaOH 1800 5000 12.3 1.54

As seen also from the results, it is understood that the reduction inthe battery capacity is suppressed by adding 100-1000 ppm of leadmonoxide in the case of the zinc powder added with 500 ppm of indium, or10-1000 ppm of lead monoxide in the case of the zinc powder added with1800 ppm of indium. The decrease in the battery capacity by the additionof lead monoxide at the high concentration is considered to be due tothe fact that needle-like crystals of lead grew on account of theexcessive addition of lead monoxide, causing a possible short circuit.

Embodiment 14

A button type silver oxide battery was manufactured in the same manneras Embodiment 13 except that a gasket of polypropylene speciallyprepared for allowing hydrogen to penetrate was used. Ten pieces of themanufactured silver oxide batteries were put into a vessel made of glassfilled with liquid paraffin in a high temperature tank, a collectingtube having graduations at an upper portion was attached, and the amountof generated hydrogen gas was measured. In this state, the mixture wasmaintained at 60° C. for 20 days, which is said to correspond to a termof about 1 year, and the hydrogen gas generation amount after 20 dayswas investigated. Results are shown in Table 6.

As understood from the foregoing Embodiments, the hydrogen generation ismild and the self-discharge is also less in the case of the sodiumhydroxide series as compared with the potassium hydroxide series withrespect to the electrolyte solution. In addition, the more the indiumcontent in the zinc powder the better results are obtained, and thesmaller the adding amount of lead monoxide is.

In the actual trial production of batteries, there is given a valuesmaller than the hydrogen gas generation amount in the experiment inEmbodiment 12. In this fact, it is considered that the copper piece usedin Embodiment 12 is different from a structure of an actual collector, apart of generated hydrogen gas has been consumed by the reduction ofsilver oxide and the like.

The method in Embodiment 12 is different in the amount order of hydrogengas generation, but it is sufficient as a method for observingsubstituted characteristics for for predicting hydrogen generation in anactual battery.

The same experiment was performed for indium compounds, tin compoundscontaining tetravalent tin, and mixtures thereof other than leadmonoxide. Results thereof are substantially the same as those in thecase of lead monoxide, and it has been found that the reduction in thebattery capacity is suppressed by adding 100-1000 ppm of the inhibitorin the case of the zinc powder added with 500 ppm of indium, or 10-1000ppm of the inhibitor in the case of the zinc powder added with 1800 ppmof indium.

In accordance with Embodiments 15-17, the effect will be explained inthe case where zinc containing not more than 4 ppm of iron and one ormore species of compounds selected from the indium compound, the tincompound containing tetravalent tin, and lead oxide as the inhibitor ofthe present invention were used.

Embodiment 15

As the zinc powder, one containing 100 ppm of gallium manufactured bythe atomization method, 200 ppm of indium, 500 ppm of lead and 450 ppmof aluminum, and further containing 5 ppm of iron was used. Theconcentration of iron in the zinc powder was adjusted by performing ironremoval by means of a magnet. The concentration after the iron removalwas confirmed by the atomic absorption method.

The hydrogen generation test was performed such that into a speciallyprepared test tube having a volume of 25 ml and graduated to indicatethe amount of gas generation there were placed 2 g of zinc powder and acopper piece of the same material as a collector having an area of 0.6cm² and a thickness of 0.1 mm, an electrolyte solution to be tested wasadded thereto to heat to 60° C., and the volume of hydrogen gasgenerated was measured for 7 days. The number of repetition of the testwas 10, and an average value thereof was used as a result. Theelectrolyte solution was prepared by making a solution in whichpotassium hydroxide was 30% by weight and zinc oxide was added up toapproximate saturation in the case of the potassium hydroxide series, ora solution in which sodium hydroxide was 25% by weight and zinc oxidewas added up to approximate saturation in the case of the sodiumhydroxide series, and a base lead monoxide or the like was added theretoas the inhibitor.

The concentration of iron in the zinc powder and the generated amount ofhydrogen gas with respect to the adding amount of the inhibitor areshown in Table 7. The adding amount of the inhibitor is shown by ppmwith respect to the electrolyte solution. Results are also shown in thehydrogen generation amount in Table 7.

TABLE 7 Hydrogen volume generated from zinc powder Content ofConcentration Hydrogen Experi- Fe in zinc of PbO in evolution mentalElectro- powder electrolyte rate No. lyte ppm ppm μL/g/day 1 KOH 5 0570.00 2 KOH 5 10 53.75 3 KOH 5 50 56.25 4 KOH 5 100 79.29 5 KOH 5 500120.85 6 KOH 5 1000 158.92 7 KOH 5 5000 284.28 8 KOH 4 0 508.94 9 KOH 410 21.14 10 KOH 4 50 16.13 11 KOH 4 100 20.15 12 KOH 4 500 45.21 13 KOH4 1000 50.56 14 KOH 4 5000 201.73 15 KOH 2 0 516.92 16 KOH 2 10 12.50 17KOH 2 50 12.50 18 KOH 2 100 14.29 19 KOH 2 500 30.21 20 KOH 2 1000 53.5721 KOH 2 5000 162.85 22 NaOH 5 0 423.85 23 NaOH 5 10 42.36 24 NaOH 5 5040.23 25 NaOH 5 100 66.34 26 NaOH 5 500 100.25 27 NaOH 5 1000 132.58 28NaOH 5 5000 278.90 29 NaOH 4 0 396.37 30 NaOH 4 10 19.36 31 NaOH 4 5012.72 32 NaOH 4 100 15.64 33 NaOH 4 500 38.38 34 NaOH 4 1000 47.25 35NaOH 4 5000 190.01 36 NaOH 2 0 43.56 37 NaOH 2 10 11.23 38 NaOH 2 5010.12 39 NaOH 2 100 12.93 40 NaOH 2 500 27.81 41 NaOH 2 1000 42.21 42NaOH 2 5000 130.10

Hydrogen gas generation results in the electrolyte solution of thepotassium hydroxide series are shown in FIG. 8. 1 in the figure is acase in which the zinc powder having a concentration of iron of 5 ppmwas used, and the hydrogen generation amount is generally large ascompared with the following two. 2 is a case in which the zinc powderhaving a concentration of iron of 4 ppm was used, and there is an effectof hydrogen generation suppression when an amount of lead monoxide ofnot less than 10 ppm was added. 3 is a case in which the zinc powderhaving a concentration of iron of 2 ppm was used, and there is ahydrogen generation suppression effect in a concentration rangeequivalent to that of 2. Especially, when the added amount of iron as animpurity was not more than 4 ppm, the effect of an added amount of leadmonoxide of not more than 100 ppm is evident, and it is possible toreduce the added amount of lead as an environmental pollution substance.

The experiment has been described in the present Embodiment in whichiron removal was performed by a magnet, and the concentration of iron islowered. However, in an experiment regarding zinc which was removed fromiron by means of purification during the production steps for zincpowder, substantially the same results were obtained.

Embodiment 16

Into a positive electrode can were added a part of an electrolytesolution and 116 mg of a pellet (silver oxide content of 98%) which wasmolded by adding a combined agent into silver oxide, and a separator ofpolyethylene and a separator of cellophane were set in place. Next, agasket of nylon was pushed and fitted into the positive electrode can,an impregnating agent, a gelling agent, 30 mg of zinc powder, aninhibitor and the like were added. The remainder of the electrolytesolution was then added dropwise, and then a negative electrode can wasset in place to seal the foregoing arrangement and 100 pieces of everykind of button type silver oxide battery was manufactured. The batterysize made of the SR621 type. The electrolyte solution was made again sothat the adding amount of lead monoxide to be an amount with respect tothe zinc amount.

They were stored at 60° C. for 20 days which is said to correspond to 1year at ordinary temperature, and the self-discharge rate was measured,results of which are shown in Table 8.

TABLE 8 Self-discharge rate of cell and hydrogen evolution rate Contentof Concentration Self- Hydrogen Experi- Fe in zinc of PbO in dischargeevolution mental Electro- powder electrolyte rate rate No. lyte ppm ppm% μL/g/day 1 KOH 5 0 13.2 0.98 2 KOH 5 10 8.7 0.76 3 KOH 5 50 7.2 0.79 4KOH 5 100 4.0 0.48 5 KOH 5 500 8.6 0.64 6 KOH 5 1000 8.5 0.77 7 KOH 55000 16.2 1.48 8 KOH 4 0 13.0 0.89 9 KOH 4 10 3.8 0.45 10 KOH 4 50 3.50.37 11 KOH 4 100 2.2 0.33 12 KOH 4 500 2.8 0.29 13 KOH 4 1000 3.9 0.4014 KOH 4 5000 17.6 1.42 15 KOH 2 0 11.0 0.82 16 KOH 2 10 2.2 0.24 17 KOH2 50 1.5 0.23 18 KOH 2 100 1.4 0.21 19 KOH 2 500 2.2 0.25 20 KOH 2 10003.5 0.33 21 KOH 2 5000 17.2 1.62 22 NaOH 5 0 10.1 0.92 23 NaOH 5 10 8.00.72 24 NaOH 5 50 5.5 0.67 25 NaOH 5 100 4.1 0.40 26 NaOH 5 500 7.4 0.6527 NaOH 5 1000 7.2 0.73 28 NaOH 5 5000 14.2 1.28 29 NaOH 4 0 9.2 0.80 30NaOH 4 10 3.7 0.35 31 NaOH 4 50 2.0 0.29 32 NaOH 4 100 2.0 0.29 33 NaOH4 500 2.2 0.26 34 NaOH 4 1000 3.2 0.41 35 NaOH 4 5000 15.2 1.31 36 NaOH2 0 7.1 0.72 37 NaOH 2 10 1.5 0.25 38 NaOH 2 50 0.8 0.19 39 NaOH 2 1000.7 0.18 40 NaOH 2 500 1.1 0.23 41 NaOH 2 1000 2.9 0.28 42 NaOH 2 50009.8 1.46

As seen also from the results, it is understood that the self-dischargerate can be suppressed to be not more than 4 a by adding 10-1000 ppm oflead monoxide in the battery using zinc powder having iron of not morethan 4 ppm. The decrease in the battery capacity by the addition of leadmonoxide at the high concentration was considered due to the fact thatneedle-like crystals of lead grew on account of excessive addition,which may cause a short circuit.

Embodiment 17

A button type silver oxide battery was manufactured in the same manneras Embodiment 16 except that a specially prepared gasket ofpolypropylene which allows hydrogen to penetrate was used. Ten pieces ofmanufactured silver oxide batteries were put into a vessel made of glassfilled with liquid paraffin in a high temperature tank, a collectingtube having graduations at the upper portion was attached, and theamount of generated hydrogen gas was measured. This state was maintainedat 60° C. for 20 days which is said to correspond to a term of about 1year, and the hydrogen gas generation amount after 20 days wasinvestigated. Results are shown in Table 8.

As understood from Embodiments, the hydrogen generation is mild and theself-discharge is also less in the case of the sodium hydroxide seriesas compared with the potassium hydroxide series with respect to theelectrolyte solution. In addition, the lower the iron content in thezinc powder is, the better the results are which are obtained, and thesmaller the added amount of lead monoxide is.

In the actual trial production of batteries, a hydrogen gas generationvalue smaller than the hydrogen gas generation amount in the experimentin Embodiment 15 is obtained. This is due to the fact that the copperpiece used in Embodiment 15 is different from the structure of an actualcollector and that a part of generated hydrogen gas has been consumed bythe reduction of silver oxide and the like.

The method in Embodiment 15 is different in the amount of order ofhydrogen gas generation, but it is sufficient as a method for observingsubstituted characteristics for predicting hydrogen generation in anactual battery.

The same experiment was performed for indium compounds, tin compoundscontaining tetravalent tin, and mixtures thereof other than leadmonoxide. Results thereof are substantially the same as those in thecase of lead monoxide, and it has been found that the self-dischargerate can be suppressed to be not more than 4% by adding 10-1000 ppm ofthe inhibitor.

In the present invention, the description has been made for iron whichis easiest to contaminate and has a high risk of hydrogen generation,however, it is understood that it is preferable to use one in whichimpurities such as nickel, cobalt, antimony and the like are reduced asmuch as possible. In addition, in the case of the negative electrodeactive material such as zinc and the like in which hydrogen generationis large, a homogeneous film is difficult to be formed due to thehydrogen generation which occurs as a competitive reaction against leaddeposition onto the surface, and the effect of lead deposition becomessmall. Thus, it is more effective to use a negative electrode activematerial in which zinc is added with indium, bismuth, lead, aluminum,gallium, calcium and the like so as to suppress the hydrogen generationto some extent.

In accordance with the following Embodiments 18-21, the effect of thecase in which the moisture in the battery is controlled will beexplained.

Embodiment 18

Into a positive electrode can were added a part of an electrolytesolution and a pellet (silver oxide content of 98%) which was molded byputting a combined agent into silver oxide, and a separator ofpolyethylene and a separator of cellophane were set in place.

Next, a gasket of specially prepared polypropylene for allowing hydrogento penetrate was pushed and fitted into the positive electrode can, andan impregnating agent, a gelling agent, zinc powder, an inhibitor andthe like were added. The remainder of the electrolyte solution was addeddropwise, and then a negative electrode can was set in place to performsealing resulting in the manufacture of a button type silver oxidebattery.

The electrolyte solution was prepared in which a base was prepared bymaking a solution in which potassium hydroxide was 30% by weight andzinc oxide was added up to approximate saturation in the case of thepotassium hydroxide series, or a solution in which sodium hydroxide was25% by weight and zinc oxide was added up to approximate saturation inthe case of the sodium hydroxide series, and the inhibitor wasoptionally added thereto. The amount of inhibitor added was 1000 ppmwith respect to the zinc weight, and it was dissolved in the electrolytesolution.

Ten pieces of the manufactured coin or button silver oxide batterieswere placed into a vessel made of glass filled with liquid paraffin in ahigh temperature tank, a collecting tube having graduations at the upperportion was attached, and the amount of generated hydrogen was measured.In this state, the vessel was maintained at 60° C. for 20 days, which issaid to correspond to a term of about 1 year, and the hydrogen gasgeneration amount and the self-discharge rate after 20 days wereinvestigated. The battery capacity was measured by connecting aresistance of 25 Ω and having it discharge. The self-discharge rate wascalculated from the change in the battery capacity before and after thestorage at 60° C. for 20 days using the same kind of batteries.

The size of the coin or button silver oxide battery manufactured andevaluated, the content of metal in the zinc powder used, the electrolytesolution, the moisture amount, the inhibitor added, and the hydrogengeneration amount and the self-discharge rate after the storage at 60°C. for 20 days are shown in Table 9 and Table 10.

TABLE 9 Hydrogen evolution rate and self-discharge rate of cell After 20After 1 year days storage storage at Amount at 60° C. room temperatureComposition of of water Hydrogen Self- Hydrogen Self- Experi- addedmetal added to evolution discharge evolution discharge mental Cell (ppmvs zinc) Electro- zinc of rate rate rate rate No. type Ga In Pb Bi Allyte 1 mg Inhibitor μl/g/day % μl/g/day % 1 SR626 500 500 500 NaOH 0.448— 0.37 3.00 0.00 3.10 2 SR626 500 500 500 KOH 0.428 — 0.39 2.50 0.002.50 3 SR626 500 500 NaOH 0.448 — 0.41 2.70 0.00 2.60 4 SR626 500 500KOH 0.428 — 0.47 2.40 0.00 2.50 5 SR626 100 200 500 450 NaOH 0.448 —0.40 2.50 0.00 2.60 6 SR626 100 200 500 450 KOH 0.428 — 0.46 2.60 0.002.60 7 SR621 500 500 500 NaOH 0.459 — 0.38 2.10 0.00 2.10 8 SR621 500500 500 KOH 0.440 — 0.40 3.10 0.00 3.30 9 SR621 500 500 NaOH 0.459 —0.43 2.80 0.00 2.70 10 SR621 500 500 KOH 0.440 — 0.45 2.70 0.00 2.70 11SR516 500 500 500 NaOH 0.476 — 0.35 2.80 0.00 2.70 12 SR516 500 500 500KOH 0.455 — 0.37 2.80 0.00 2.60 13 SR516 500 500 NaOH 0.476 — 0.41 2.900.00 2.50 14 SR516 500 500 KOH 0.455 — 0.45 3.00 0.00 2.90 15 SR527 500500 500 NaOH 0.488 — 0.38 2.70 0.00 2.80 16 SR527 500 500 500 KOH 0.463— 0.39 2.60 0.00 2.60 17 SR527 500 500 NaOH 0.488 — 0.43 2.50 0.00 2.4018 SR527 500 500 KOH 0.463 — 0.47 2.70 0 00 2 60 19 SR726 500 500 500NaOH 0.441 — 0.35 2.10 0.00 2.50

TABLE 10 Hydrogen evolution rate and self-discharge rate of cell After20 After 1 year days storage storage at Amount at 60° C. roomtemperature Composition of of water Hydrogen Self- Hydrogen Self-Experi- added metal added to evolution discharge evolution dischargemental Cell (ppm vs zinc) Electro- zinc of rate rate rate rate No. typeGa In Pb Bi Al lyte 1 mg Inhibitor μl/g/day % μl/g/day % 20 SR726 500500 500 KOH 0.423 — 0.36 1.50 0.00 2.00 21 SR726 500 500 NaOH 0.441 —0.37 1.90 0.00 1.80 22 SR726 500 500 KOH 0.423 — 0.45 2.20 0.00 2.10 23SR1120 500 500 500 NaOH 0.441 — 0.35 1.90 0.00 2.10 24 SR1120 500 500500 KOH 0.423 — 0.34 2.60 0.00 2.10 25 SR1120 500 500 NaOH 0.441 — 0.372.30 0.00 2.20 26 SR1120 500 500 KOH 0.423 — 0.38 2.40 0.00 2.50 27SR626 500 500 500 NaOH 0.448 Indium sulfate 0.33 2.50 0.00 2.50 28 SR626500 500 500 KOH 0.428 Indium sulfate 0.35 2.30 0.00 2.60 29 SR626 500500 NaOH 0.448 Indium sulfate 0.38 2.70 0.00 2.50 30 SR626 500 500 KOH0.428 Indium sulfate 0.42 2.80 0.00 2.90 31 SR626 100 200 500 450 NaOH0.448 Indium sulfate 0.37 2.70 0.00 2.70 32 SR626 100 200 500 450 KOH0.428 Indium sulfate 0.41 2.80 0.00 2.80 33 SR626 500 NaOH 0.448 Indiumsulfate 0.39 2.80 0.00 2.70 34 SR626 500 KOH 0.428 Indium sulfate 0.422.60 0.00 2.60 35 SR626 500 NaOH 0.448 Indium sulfamate 0.42 2.70 0.002.50 36 SR626 500 KOH 0.428 Indium sulfamate 0.45 2.70 0.00 2.40 37SR626 500 NaOH 0.448 PbO 0.42 2.50 0.00 2.90 38 SR626 500 KOH 0.428 PbO0.44 2.50 0.00 2.20

In Table 9 and Table 10, with respect to the added metal composition,the weight of zinc is expressed by ppm. The moisture amount isrepresented in terms of how many mg of water was contained with respectto 1 mg of zinc. The unit for the hydrogen generation amount is μ/g/day,the hydrogen generation amount per one day with respect to the zincamount is shown at the right of each of the columns for 60° C. for 20days and ordinary temperature for 1 year in the table, and the unit forthe self-discharge rate is shown by %. In-sulfate indicates indiumsulfate, In-sulfamate indicates indium sulfamate, and PbO indicates leadoxide. It is,understood that all are suppressed to be not more than 0.03μL/g/day when the hydrogen generation amount is calculated into a valueat ordinary temperature. In addition, it was also possible to make theself-discharge rate to be not more than 4%/year.

Embodiment 19

In order to know whether or not the storage at 60° C. for 20 days inEmbodiment 18 corresponds to 1 year at ordinary temperature, a test for1 year was actually performed.

The gasket used in Embodiment 18 was exchanged into one made of nylonbeing used in ordinary production of silver oxide batteries, and coin orbutton silver oxide batteries were manufactured in the same manner. Tenpieces of the manufactured silver oxide batteries were placed into avessel made of glass filled with liquid paraffin in a high temperaturetank maintained at 25° C., and a collecting tube for generating hydrogengas was attached at the upper portion. This state was maintained for 1year, and the hydrogen generation amount and the self-discharge rateafter 1 year were investigated. The measurement method was the same asthat in Embodiment 18. Results of the hydrogen generation amount and theself-discharge rate are shown at the right ends in Table 9 and Table 10.

As a result of the test, no gas generation was observed in any sample.This is considered to be due to the fact that a minute amount ofhydrogen generated in the battery was consumed by the reduction ofsilver oxide. The self-discharge rate was substantially the same asthose preserved at 60° C. for 20 days, and all had self-discharge valuesof not more than 4%.

Embodiment 20

As for the electrolyte solution, in the case of the potassium hydroxideseries, zinc oxide was added to potassium hydroxide up to approximatesaturation was used. The amount of added electrolyte solution per 1 mgof zinc was changed from 0.37 to 0.96 mg which was from 0.25 to 0.65 mgas calculated into the amount of water, using zinc containing 500 ppm ofeach of indium, lead and bismuth and a gasket of polypropylene in thesame manner as Embodiment 18, a silver oxide battery of the SR626 sizewas made, and the storage test was performed at 60° C. for 20 days.

The hydrogen generation amount with respect to the added amount of wateris shown in FIG. 9. The hydrogen generation amount indicates an amountgenerated from 1 g of zinc per one day, and the unit is μL/g/day.According to the result, it is understood that when the amount of wateris not less than 0.31 mg, the hydrogen generation amount is lowered tonot more than 0.54 μL/g/day (0.03 μL/g/day as calculated into a value atorninary temperature). In addition, when the amount of water was notless than 0.57 mg, the occurrence of liquid leakage was observed.

In the same manner, when an electrolyte solution of the sodium hydroxideseries was used, the amount of the electrolyte solution added per 1 mgof zinc was changed from 0.36 to 0.92 mg which is from 0.25 to 0.65 mgwhen it is calculated into the amount of water, and the storage test wasperformed at 60° C. for 20 days. A result is.shown in FIG. 10. It isunderstood that when the amount of water is not less than 0.32 mg, thehydrogen generation amount is lowered to not more than 0.54 μL/g/day. Inaddition, when the amount of water became not less than 0.59 mg, theoccurrence of liquid leakage was observed.

Namely, it is desirable that the amount of water to be added per 1 mg ofzinc is 0.31-0.57 mg when the electrolyte solution is the potassiumhydroxide series and 0.32-0.59 mg when it is the sodium hydroxideseries.

Embodiment 21

In order to know whether or not there is actually a problem in the rangeof the amount of water in which the hydrogen generation is not more than0.54 μL/g/day and there is no liquid leakage in Embodiment 20, thestorage test at ordinary temperature for 1 year was performed and triedusing the method in Embodiment 19. In the case of the potassiumhydroxide series, the electrolyte solution was added in an amount suchthat the amount of water added per 1 mg of zinc became 0.31, 0.44 and0.57 mg. In the same manner, in the case of the sodium hydroxide series,the electrolyte solution was added so that the amount of water became0.32, 0.45 and 0.59 mg. A nylon gasket was used in the same manner asEmbodiment 20, and 10 pieces of silver oxide batteries weremanufactured, respectively. According to the results of the storage testat ordinary temperature for 1 year for the manufactured silver oxidebatteries, there was no hydrogen generation, the self-discharge rateswere also not more than 4% for all batteries, and it has been found thatthere is no practical problem.

In accordance with Embodiments 22-24, the effect of the case in whicheach technique is combined will be explained.

Before actually investigating characteristics with batteries, aspecially prepared test tube was used to investigate the amount ofhydrogen gas generated from each of the inhibitors and the plated copperplates. The method therefor will be described hereinafter.

Into the specially prepared test tube having a volume of 25 ml andgraduated to determine the gas generation amount there was placed 2 g ofzinc powder containing 500 ppm of each of bismuth, indium and leadmanufactured by the atomization method and a copper piece of the samematerial as a collector having an area of 0.6 cm² and a thickness of 0.1mm. An electrolyte solution to be tested was added thereto to heat to60° C., and the volume of generated hydrogen gas was measured for 7days. The number of test repetitions was 10, and an average valuethereof was used as a result. The electrolyte solution was prepared bymaking a solution in which potassium hydroxide was 30% by weight andzinc oxide was added up to approximate saturation in the case of thepotassium hydroxide series, or a solution in which sodium hydroxide was25% by weight and zinc oxide was added up to approximate saturation inthe case of the sodium hydroxide series as a base. An inhibitor wasoptionally added thereto.

Embodiment 22

The hydrogen generation from zinc was measured by the 73 combination ofa copper plate coated by electric plating and the substitution platingand the inhibitor. The plating treatment is shown hereinafter.

Indium (In) plating

method: electric plating

plating bath: 25° C. indium sulfate 60 g/l sodium sulfate 10 g/l

plating film thickness: 0.3 μm

Tin (Sn) plating method: electric plating

plating bath: 70° C. potassium stannate 100 g/l potassium hydroxide 15g/l potassium acetate 5 g/l

plating film thickness: 0.3 μm

Zinc indium (Zn-In) plating

method: contact plating (copper plate and zinc are placed into thefollowing plating bath heated to 60° C. and left for 1 hour)

plating bath: KOH 30% ZnO saturation indium sulfate 0.3%

plating film thickness: 0.3 μm

The type of plating performed onto the copper plate and the hydrogen gasgeneration measurement result with respect to the inhibitor used areshown for the case in which an electrolyte solution of the KOH serieswas used in Table 11 and that of the NaOH type was used in Table 12.

TABLE 11 Hydrogen evolution rate with plated copper plate HydrogenExperi- Inhibitor evolution mental Kind of Electro- (concentration: rateNo. plating lyte 100 ppm) μL/g/day 1 In KOH — 31.43 2 In KOH Indiumsulfate 14.28 3 In KOH Indium sulfamate 12.41 4 In KOH Indium hydroxide16.73 5 In KOH Lead oxide 17.85 6 In KOH Barium hydroxide 8.57 7 In KOHCarbon fluoride.POE 12.14 8 Sn KOH — 35.78 9 Sn KOH Indium sulfate 16.1110 Sn KOH Indium sulfamate 17.72 11 Sn KOH Indium hydroxide 16.53 12 SnKOH Lead oxide 17.91 13 Sn KOH Barium hydroxide 10.89 14 Sn KOH Carbonfluoride.POE 14.38 15 Zn.In KOH — 32.34 16 Zn.In KOH Indium sulfate15.27 17 Zn.In KOH Indium sulfamate 13.35 18 Zn.In KOH Indium hydroxide18.83 19 Zn.In KOH Lead oxide 16.82 20 Zn.In KOH Barium hydroxide 11.3021 Zn.In KOH Carbon fluoride.POE 13.01

TABLE 12 Hydrogen evolution rate with plated copper plate HydrogenExperi- Inhibitor evolution mental Kind of Electro- (concentration: rateNo. plating lyte 100 ppm) μL/g/day 22 In NaOH — 29.41 23 In NaOH Indiumsulfate 14.75 24 In NaOH Indium sulfamate 10.58 25 In NaOH Indiumhydroxide 15.37 26 In NaOH Lead oxide 14.14 27 In NaOH Barium hydroxide7.82 28 In NaOH Carbon fluoride.POE 9.34 29 Sn NaOH — 30.10 30 Sn NaOHIndium sulfate 15.03 31 Sn NaOH Indium sulfamate 15.28 32 Sn NaOH Indiumhydroxide 15.38 33 Sn NaOH Lead oxide 14.53 34 Sn NaOH Barium hydroxide8.72 35 Sn NaOH Carbon fluoride.POE 12.43 36 Zn.In NaOH — 32.83 37 Zn.InNaOH Indium sulfate 14.98 38 Zn.In NaOH Indium sulfamate 13.19 39 Zn.InNaOH Indium hydroxide 14.13 40 Zn.In NaOH Lead oxide 14.27 41 Zn.In NaOHBarium hydroxide 9.98 42 Zn.In NaOH Carbon fluoride.POE 9.84

The concentration of the inhibitor is shown by a value with respect tothe electrolyte solution. As the surfactant of the fluorocarbon(carbonfluoride)-polyoxyethylene (POE) series, one having a carbon number offluorocarbon of 10 and a polymerization degree of POE of 50 was used.Usually, the same effect can be obtained if one having a carbon numberof fluorocarbon of 4-20 and a polymerization degree of POE of 30-100 isused.

As compared with the Embodiment in which no inhibitor is added, in theEmbodiment in which the inhibitor of the present invention is added, thehydrogen gas generation amount decreases from about ⅓ to 112, and it isunderstood that there is an effect in relation to suppression of thehydrogen gas generation. The difference due to the plating or theinhibitor is not presented so much. In addition, the hydrogen gasgeneration amount with respect to the number of test days is shown inFIG. 11 as for the case in which indium plated copper plates are used.As for the indium compound, only indium sulfate is shown in the figure.

In the present Embodiment, the result of the case using one having aplating film thickness of 0.3 μm has been shown, however, in practice,also when one having a film thickness of 0.1-1 μm was used, there waslittle difference in the result.

Comparative example 2

For comparison, an experiment was performed using non-plated copperplates in the same procedure as Embodiment 22. Experiment results areshown in Table 13 and FIG. 12.

TABLE 13 Hydrogen evolution rate with unplated copper plate HydrogenExperi- Inhibitor evolution mental Electro- (concentration: rate No.lyte 100 ppm) μL/g/day 1 KOH — 516.00 2 KOH Indium sulfate 30.56 3 KOHIndium sulfamate 28.73 4 KOH Indium hydroxide 29.07 5 KOH Lead oxide24.15 6 KOH Barium hydroxide 480.32 7 KOH Carbon fluoride.POE 465.29 8NaOH — 450.24 9 NaOH Indium sulfate 25.86 10 NaOH Indium sulfamate 27.5911 NaOH Indium hydroxide 25.48 12 NaOH Lead oxide 20.25 13 NaOH Bariumhydroxide 400.44 14 NaOH Carbon fluoride.POE 392.91

It is understood that in the case in which no inhibitor is added butbarium hydroxide or the surfactant of the fluorocarbon-polyoxyethyleneseries is added, the hydrogen gas generation amount increasesexponentially with respect to the number of test days. On the otherhand, it is understood that in the case where indium sulfate and leadoxide are added, the generation of hydrogen gas is suppressed. This isdue to the fact that the compound of indium or lead function to coat thecopper plate, but barium hydroxide and the surfactant have no suchfunction.

Embodiment 23

Using a copper plate plated in the same manner as Embodiment 22, thehydrogen gas generation in the case where inhibitors have been combinedwas measured using an electrolyte solution of the KOH series. Resultsare shown in Table 14.

TABLE 14 Hydrogen evolution rate with indium plated copper plate andinhibitor Hydrogen Experi- Concentration of inhibitor ppm evolutionmental Indium Lead Indium Carbon rate No. sulfate oxide hydroxidefluoride-POE μL/g/day 43 100 100 0 0 15.82 44 100 0 100 0 10.10 45 100 00 100 13.41 46 0 100 100 0 14.64 47 0 100 0 100 15.54 48 0 0 100 10012.47 49 100 100 100 0 14.87 50 100 100 0 100 12.21 51 100 0 100 10013.05 52 100 100 100 100 13.94

In the column for the inhibitor in the table, the concentration of eachinhibitor added to the electrolyte solution with respect to theelectrolyte solution is shown. It is understood that the hydrogen gasgeneration is of a low level similar to the foregoing Embodiments, andthere is no substantial bad effect even when a plurality of inhibitorsare used.

Next, a battery was actually manufactured, and the effects of theplating on the collector and the inhibitor were investigated.

Embodiment 24

Into a positive electrode can were added a part of an electrolytesolution and 116 mg of a pellet (silver oxide content of 98%) which wasmolded by putting a combined agent into which silver oxide, and aseparator of polyethylene and a separator of cellophane were set inplace. Next, a gasket of nylon was pushed and fitted into the positiveelectrode can, and an impregnating agent, a gelling agent, and 30 mg ofzinc powder were added. The remainder of the electrolyte solution wasoptionally added and an inhibitor was added dropwise. Then a negativeelectrode can was set in place to perform sealing to manufacture 100pieces for every kind of button type silver oxide batteries.

The type and the film thickness of the plating onto the negativeelectrode can, the type and the concentration of the added inhibitor,the closed circuit voltage and the self-discharge rate are shown inTables 15 and 16.

TABLE 15 Characteristics of cell with KOH electrolyte Concentration ofinhibitor Self-discharge Closed circuit ppm rate % voltage V Experi-Kind Carbon A part- A part- mental of Indium Lead barium fluoride Freshdischarge Fresh discharge No. plating sulfate oxide hydroxide POE cellcell cell cell 53 — 0 0 0 0 5.6 9.4 1.159 1.180 54 In 0 0 0 0 4.5 6.21.165 1.192 55 In 1000 0 0 0 2.6 2.7 1.169 1.198 56 In 0 1000 0 0 2.72.8 1.168 1.197 57 In 0 0 1000 0 2.5 4.9 1.185 1.198 58 In 0 0 0 10002.9 5.1 1.165 1.185 59 In 1000 1000 0 0 2.5 2.6 1.168 1.198 60 In 1000 01000 0 2.4 2.6 1.185 1.239 61 In 1000 0 0 1000 2.5 2.7 1.168 1.198 62 In0 1000 0 1000 2.6 2.7 1.167 1.197 63 In 0 1000 1000 0 2.7 2.7 1.1671.238 64 In 0 1000 1000 1000 2.6 2.6 1.186 1.238 65 In 1000 1000 1000 02.6 2.7 1.186 1.129 66 In 1000 1000 0 1000 2.7 2.7 1.168 1.198 67 In1000 0 1000 1000 2.6 2.6 1.185 1.238 68 In 1000 1000 1000 1000 2.6 2.71.185 1.238 69 Sn 0 0 0 0 5.7 10.5  1.160 1.181 70 Sn 1000 0 0 0 4.7 6.81.166 1.193 71 Sn 0 1000 0 0 2.7 2.7 1.171 1.198 72 Sn 0 0 1000 0 2.72.8 1.170 1.198 73 Sn 0 0 0 1000 2.6 5.0 1.186 1.197 74 Sn 1000 1000 0 03.0 5.3 1.165 1.187 75 Sn 1000 0 1000 0 2.6 2.7 1.169 1.199 76 Sn 1000 00 1000 2.4 2.5 1.187 1.240 77 Sn 0 1000 0 1000 2.4 2.8 1.169 1.200 78 Sn0 1000 1000 0 2.5 2.6 1.168 1.197 79 Sn 0 1000 1000 1000 2.7 2.8 1.1691.240 80 Sn 1000 1000 1000 0 2.5 2.8 1.188 1.240 81 Sn 1000 1000 0 10002.8 2.8 1.186 1.131 82 Sn 1000 0 1000 1000 2.8 2.8 1.170 1.199 83 Sn1000 1000 1000 1000 2.7 2.6 1.186 1.239 84 Zn—In 0 0 0 0 5.7 9.8 1.1661.193 85 Zn—In 1000 0 0 0 4.9 7.1 1.170 1.199 86 Zn—In 0 1000 0 0 2.82.7 1.170 1.197 87 Zn—In 0 0 1000 0 2.9 2.9 1.187 1.199 88 Zn—In 0 0 01000 2.6 4.8 1.166 1.184 89 Zn—In 1000 1000 0 0 2.9 5.3 1.168 1.200 90Zn—In 1000 0 1000 0 2.6 2.7 1.186 1.240 91 Zn—In 1000 0 0 1000 2.6 2.71.170 1.199 92 Zn—In 0 1000 0 1000 2.6 2.9 1.168 1.199 93 Zn—In 0 10001000 0 2.7 2.7 1.168 1.238 94 Zn—In 0 1000 1000 1000 2.9 2.9 1.188 1.24095 Zn—In 1000 1000 1000 0 2.8 2.8 1.188 1.131 96 Zn—In 1000 1000 0 10002.6 2.9 1.168 1.200 97 Zn—In 1000 0 1000 1000 2.9 2.8 1.187 1.239 98Zn—In 1000 1000 1000 1000 2.7 2.7 1.186 1.239

TABLE 16 Characteristics of cell with NaOH electrolyte Concentration ofinhibitor Self-discharge Closed circuit ppm rate % voltage V Experi-Kind Carbon A part- A part- mental of Indium Lead barium fluoride Freshdischarge Fresh discharge No. plating sulfate oxide hydroxide POE cellcell cell cell 99 — 0 0 0 0 5.3 9.0 1.158 1.180 100 In 0 0 0 0 4.2 5.91.164 1.193 101 In 1000 0 0 0 2.2 2.3 1.169 1.199 102 In 0 1000 0 0 2.22.4 1.167 1.197 103 In 0 0 1000 0 2.2 4.6 1.187 1.199 104 In 0 0 0 10002.5 4.8 1.166 1.186 105 In 1000 1000 0 0 2.1 2.3 1.169 1.199 106 In 10000 1000 0 1.9 2.2 1.186 1.239 107 In 1000 0 0 1000 2.0 2.5 1.169 1.197108 In 0 1000 0 1000 2.3 2.6 1.169 1.196 109 In 0 1000 1000 0 2.3 2.21.169 1.238 110 In 0 1000 1000 1000 2.0 2.1 1.187 1.237 111 In 1000 10001000 0 2.4 2.4 1.186 1.131 112 In 1000 1000 0 1000 2.4 2.3 1.170 1.198113 In 1000 0 1000 1000 2.3 2.0 1.177 1.239 114 In 1000 1000 1000 10002.2 2.5 1.186 1.237 115 Sn 0 0 0 0 5.5 10.2  1.160 1.183 116 Sn 1000 0 00 4.4 6.5 1.167 1.194 117 Sn 0 1000 0 0 2.4 2.3 1.173 1.199 118 Sn 0 01000 0 2.5 2.6 1.171 1.200 119 Sn 0 0 0 1000 2.4 4.7 1.186 1.197 120 Sn1000 1000 0 0 2.7 5.0 1.166 1.186 121 Sn 1000 0 1000 0 2.2 2.5 1.1701.201 122 Sn 1000 0 0 1000 2.1 2.3 1.187 1.241 123 Sn 0 1000 0 1000 2.22.5 1.170 1.201 124 Sn 0 1000 1000 0 2.2 2.2 1.167 1.198 125 Sn 0 10001000 1000 2.2 2.5 1.171 1.241 126 Sn 1000 1000 1000 0 2.3 2.6 1.1891.242 127 Sn 1000 1000 0 1000 2.6 2.5 1.187 1.133 128 Sn 1000 0 10001000 2.6 2.3 1.172 1.200 129 Sn 1000 1000 1000 1000 2.4 2.4 1.186 1.239130 Zn—In 0 0 0 0 5.3 9.5 1.168 1.194 131 Zn—In 1000 0 0 0 4.6 6.6 1.1711.201 132 Zn—In 0 1000 0 0 2.4 2.5 1.172 1.198 133 Zn—In 0 0 1000 0 2.52.7 1.187 1.200 134 Zn—In 0 0 0 1000 2.3 4.6 1.168 1.185 135 Zn—In 10001000 0 0 2.6 5.0 1.170 1.200 136 Zn—In 1000 0 1000 0 2.3 2.3 1.188 1.241137 Zn—In 1000 0 0 1000 2.2 2.4 1.171 1.198 138 Zn—In 0 1000 0 1000 2.42.5 1.169 1.199 139 Zn—In 0 1000 1000 0 2.6 2.5 1.167 1.237 140 Zn—In 01000 1000 1000 2.7 2.6 1.187 1.242 141 Zn—In 1000 1000 1000 0 2.4 2.31.188 1.132 142 Zn—In 1000 1000 0 1000 2.6 2.7 1.167 1.201 143 Zn—In1000 0 1000 1000 2.6 2.6 1.189 1.240 144 Zn—In 1000 1000 1000 1000 2.52.5 1.186 1.240

The inhibitor concentration in the table indicates a value with respectto the zinc weight. The measurement of the self-discharge rate wasperformed after maintaining it at 60° C. for 20 days, which is said tocorrespond to 1 year.

The self-discharge rate after partial discharge was measured by beingleft at 60° C. for 20 days after 50% depth discharge (partialdischarge). The closed circuit voltage was measured at −10° C. beforedischarge and after partial discharge.

As compared with the Embodiments of no addition of inhibitors(Embodiments No. 54, 69 and 84 in Table 15 and Embodiments No. 100, 115and 130 in Table 16), the Embodiments in which inhibitors have beenadded have small self-discharge rates. With respect to the partialdischarge, in the case of those added with one of the type for coatingthe negative electrode can which comprises copper, such as indiumsulfate and lead monoxide, the self-discharge rate is improved. It isunderstood that the closed circuit voltage becomes high in those addedwith barium hydroxide. It is understood from the table that when theinhibitor of the coating type and barium hydroxide are added, theself-discharge rate before discharge, the self discharge rate afterpartial discharge, and the closed circuit voltage are improved. In thepresent experiment, a behavior in which the closed circuit voltage afterpartial discharge becomes higher than that before discharge has beenobserved which is opposite to a case using mercurated zinc. The causethereof is now under investigation.

The plating onto the negative electrode can was performed in the samemanner as Embodiment 22, and results for each film thickness of 0.3 μmhave been shown. There was little difference in the result even whenthose having a film thickness of 0.1-1 μm were used.

Further, with a battery manufactured using an electrolyte of the KOHtype and a negative electrode can applied with indium plating, theself-discharge rate after a lapse corresponding to 1 year and theself-discharge rate after partial discharge with respect to theinhibitor concentration were measured.

Results are shown in FIGS. 13 and 14. Provided that the practical rangeis not more than about 3% of the self-discharge rate, it has been foundthat the effect is provided for indium sulfate of 50-5000 ppm, for leadmonoxide of 20-5000 ppm, for barium hydroxide of not less than 50 ppm,and for the fluorocarbon-polyoxyethylene type surfactant of not lessthan 100 ppm as the concentration with respect to zinc. With respect tothe self-discharge rate after 50% depth discharge, the effect wasprovided for indium sulfate of 50-5000 ppm, and for lead monoxide of20-5000 ppm. The effect is not provided so much after partial dischargefor barium hydroxide, and the fluorocarbon-polyoxyethylene seriessurfactant. The result has been shown in the case of indium sulfate forindium compounds, however, the same effect was also exhibited for othercompounds in substantially the same concentration range. In addition,even when an electrolyte solution of the NaOH series and other negativeelectrode can plating were used, the concentration range of theinhibitor exhibiting the effect was substantially the same.

In accordance with Embodiments 25-29, the effect of the case combiningeach technique will be explained. In Embodiments 22-24, the evaluationwas made using combinations in which the surfactants were changed. Inthe trial production of batteries, the evaluation was made also bychanging the type of zinc.

Before actually investigating characteristics using batteries, aspecially prepared test tube was used to investigate the amount ofhydrogen gas generated from each of the inhibitors and plated copperplates. The method therefor will be described hereinafter.

Into the specially prepared test tube having a volume of 25 ml andgraduated to determine the gas generation amount there were addedbeforehand 2 g of zinc powder containing 500 ppm of each of bismuth,indium and lead manufactured by the atomization method and a copperpiece of the same material as a collector having an area of 0.6 cm² anda thickness of 0.1 mm. An electrolyte solution to be tested was addedthereto and heated to 60° C., and the volume of generated hydrogen gaswas-measured for 7 days. The number of test repetitions was 10, and anaverage value thereof was used as a result. The electrolyte solution wasprepared such as by making a solution in which potassium hydroxide was30% by weight and zinc oxide was added up to approximate saturation inthe case of the potassium hydroxide type, or a solution in which sodiumhydroxide was 25% by weight and zinc oxide was added up to approximatesaturation in the case of the sodium hydroxide type, as a haze and aninhibitor was optionally added thereto.

Embodiment 25

The hydrogen generation from zinc was measured by the combination of acopper plate coated by electric plating and the substitution plating andthe inhibitor. The plating treatment is shown hereinafter.

Indium (In) plating

method: electric plating

plating bath: indium sulfate 60 g/l, sodium sulfate 10 g/l, 25° C.

plating film thickness: 0.3 μm

Tin (Sn) plating

method: electric plating

plating bath: potassium stannate 100 g/l, potassium hydroxide 15 g/l,potassium acetate 5 g/l, 70° C.

planting film thickness: 0.3 μm

zinc indium (Zn-In) plating

method: contact plating; copper plate and zinc are added into thefollowing plating bath heated to 60° C. and left for 1 hour

plating bath: KOH 30%, ZnO saturation, indium sulfate 0.3%

plating film thickness: 0.3 μm

The plating onto the copper plate and the hydrogen gas generationmeasurement result with respect to the inhibitor are shown for the caseusing the electrolyte solution of the KOH series in Table 17, while thecase of the NaOH series is shown in Table 18. The concentration of theinhibitor is shown by a value with respect to the electrolyte solution.

TABLE 17 Hydrogen evolution rate with plated copper plate HydrogenExperi- Inhibitor evolution mental Kind of Electro- (concentration: rateNo. plating lyte 100 ppm) μL/g/day 1 In KOH — 31.43 2 In KOH Indiumsulfate 14.28 3 In KOH Indium sulfamate 12.41 4 In KOH Indium hydroxide16.73 5 In KOH Lead oxide 17.85 6 In KOH Barium hydroxide 8.57 7 In KOHPOERA 8.42 8 Sn KOH — 35.78 9 Sn KOH Indium sulfate 16.11 10 Sn KOHIndium sulfamate 17.72 11 Sn KOH Indium hydroxide 16.53 12 Sn KOH Leadoxide 17.91 13 Sn KOH Barium hydroxide 10.89 14 Sn KOH POERA 10.02 15Zn.In KOH — 32.34 16 Zn.In KOH Indium sulfate 15.27 17 Zn.In KOH Indiumsulfamate 13.35 18 Zn.In KOH Indium hydroxide 18.83 19 Zn.In KOH Leadoxide 16.82 20 Zn.In KOH Barium hydroxide 11.30 21 Zn.In KOH POERA 10.98

TABLE 18 Hydrogen evolution rate with plated copper plate HydrogenExperi- Inhibitor evolution mental Kind of Electro- (concentration: rateNo. plating lyte 100 ppm) μL/g/day 22 In NaOH — 29.41 23 In NaOH Indiumsulfate 14.75 24 In NaOH Indium sulfamate 10.58 25 In NaOH Indiumhydroxide 15.37 26 In NaOH Lad oxide 14.14 27 In NaOH Barium hydroxide7.82 28 In NaOH POERA 8.13 29 Sn NaOH — 30.10 30 Sn NaOH Indium sulfate15.03 31 Sn NaOH Indium sulfamate 15.28 32 Sn NaOH Indium hydroxide15.38 33 Sn NaOH Lead oxide 14.53 34 Sn NaOH Barium hydroxide 8.72 35 SnNaOH POERA 9.52 36 Zn · In NaOH — 32.83 37 Zn · In NaOH Indium sulfate14.98 38 Zn · In NaOH Indium sulfamate 13.19 39 Zn · In NaOH Indiumhydroxide 14.13 40 Zn · In NaOH Lead oxide 14.27 41 Zn · In NaOH Bariumhydroxide 9.98 42 Zn · In NaOH POERA 8.95

Polyoxyethylene alkylamide is one (represented by POERA in the table andthe figure) in which two polyoxyethylenes (POE) are bonded to thenitrogen in the alkyl group through an amide bond. In this case, a POERAhaving a carbon number of the alkyl group of 11 and a polymerizationdegree of POE of 15 was used. Usually, when a POERA having a carbonnumber of the alkyl group of 3-30 and a polymerization degree of POE of2-50 is used, the same effect is obtained.

As compared with an example in which no inhibitor is added, the case inwhich the inhibitor of the present invention is added the hydrogen gasgeneration amount decreases from about ⅓ to ½, and it is understood thatthere is an effect in relation to suppression of the hydrogen gasgeneration. The difference due to the plating or the inhibitor is notpresented so much. In addition, the hydrogen gas generation amount withrespect to the number of test days is shown in FIG. 15 as themeasurement result of the case using indium plated copper plates. As forthe indium compound, only indium sulfate is shown in the figure.

In the present Embodiment, the result of the case using a plating filmthickness of 0.3 μm has been shown, however, in practice, also when afilm thickness of 0.1-1 μm was used, there was little difference in theresult.

Comparative example 3

For comparison, an experiment was performed using non-plated copperplates in the same procedure as Embodiment 25. Experiment results areshown in Table 19 and FIG. 16.

TABLE 19 Hydrogen evolution rate with unplated copper plate HydrogenInhibitor evolution Example Electro- (concentration: rate No. lyte 100ppm) μL/g/day 1 KOH — 516.00 2 KOH Indium sulfate 30.56 3 KOH Indiumsulfamate 28.73 4 KOH Indium hydroxide 29.07 5 KOH Lead oxide 24.15 6KOH Barium hydroxide 480.32 7 KOH Carbon fluoride.POE 432.19

It is understood that in the case in which no inhibitor was added bariumhydroxide or the surfactant of the fluorocarbon-polyoxyethlene serieswas added, the hydrogen gas generation amount increased exponentiallywith respect to the number of test days. On the other hand, it isunderstood that in the case in which indium sulfate and lead oxide wereadded, the generation of hydrogen gas is suppressed. This is due to thefact that the compound of indium or lead function to coat the copperplate, but barium hydroxide and the surfactant do not effectivelyperform such function.

Embodiment 26

Using a copper plate plated in the same manner as Example 25, thehydrogen gas generation in the case of the use of a combination ofinhibitors was measured using an electrolyte solution of the KOH type.Results are shown in Table 20.

TABLE 20 Hydrogen evolution rate with indium plated copper plate andinhibitor Hydrogen Experi- Concentration of inhibitor ppm evolutionmental Indium Lead Indium rate No. sulfate oxide hydroxide POERAμL/g/day 43 100 100 0 0 15.82 44 100 0 100 0 10.10 45 100 0 0 100 12.2846 0 100 100 0 14.64 47 0 100 0 100 15.40 48 0 0 100 100 9.28 49 100 100100 0 14.87 50 100 100 0 100 12.12 51 100 0 100 100 8.88 52 100 100 100100 8.54

In the column for the inhibitor in the table, the concentration of eachinhibitor added to the electrolyte solution with respect to theelectrolyte solution is shown. It is understood that the hydrogen gasgeneration is at a low-level in the same manner as in the previousExample, and there is no substantial bad effect even when a plurality ofinhibitors are used. Especially, the hydrogen gas generation is less inthe case in which barium hydroxide and polyoxyethylene alkylamide aresimultaneously added.

Next, a battery was actually manufactured, and the effects of theplating on the collector or the inhibitor were investigated.

Embodiment 27

Into a positive electrode can were added a part of an electrolytesolution and 116 mg of a pellet (silver oxide content of 98%) in whichsilver oxide was added and molded with a combined agent, and a separatorof polyethylene and a separator of cellophane were placed in the can.Next, a gasket of nylon was pushed and fitted into the positiveelectrode can, and the can was filled with an impregnating agent, agelling agent, and 30 mg of zinc powder. The remainder of theelectrolyte solution was optionally added and an inhibitor was addeddropwise. Then a negative electrode can was sealed and 100 pieces foreach kind of button type silver oxide batteries were manufactured.

A zinc powder was used containing 130 ppm of bismuth, 500 ppm of indiumand 30 ppm of aluminum manufactured by atomization.

The type and the film thickness of the plating onto the negativeelectrode can, the type and the concentration of the added inhibitor,the closed circuit voltage and the self-discharge rate are shown inTables 21 and 22.

TABLE 21 Characteristics of cell with KOH electrolyte ConcentrationSelf-discharge Closed circuit of inhibitor rate % voltage V Experi- Kindppm A part- A part- mental of Indium Lead barium Fresh discharge Freshdischarge No. plating sulfate oxide hydroxide POERA cell cell cell cell53 — 0 0 0 0 5.8 9.9 1.158 1.179 54 In 0 0 0 0 4.3 5.9 1.165 1.192 55 In1000 0 0 0 2.7 2.7 1.169 1.198 56 In 0 1000 0 0 2.7 2.8 1.168 1.197 57In 0 0 1000 0 2.5 4.9 1.186 1.198 58 In 0 0 0 1000 2.6 5.0 1.165 1.18559 In 1000 1000 0 0 2.5 2.6 1.168 1.197 60 In 1000 0 1000 0 2.4 2.61.186 1.239 61 In 1000 0 0 1000 2.4 2.5 1.168 1.199 62 In 0 1000 0 10002.4 2.6 1.168 1.197 63 In 0 1000 1000 0 2.6 2.7 1.167 1.238 64 In 0 10001000 1000 2.4 2.4 1.188 1.239 65 In 1000 1000 1000 0 2.6 2.6 1.186 1.24066 In 1000 1000 0 1000 2.5 2.6 1.170 1.200 67 In 1000 0 1000 1000 2.32.5 1.185 1.240 68 In 1000 1000 1000 1000 2.4 2.4 1.186 1.238 69 Sn 0 00 0 4.7 6.8 1.167 1.193 70 Sn 1000 0 0 0 2.8 2.7 1.168 1.198 71 Sn 01000 0 0 2.7 2.8 1.170 1.199 72 Sn 0 0 1000 0 2.6 5.0 1.187 1.199 73 Sn0 0 0 1000 2.6 5.1 1.165 1.185 74 Sn 1000 1000 0 0 2.6 2.7 1.168 1.19775 Sn 1000 0 1000 0 2.4 2.5 1.187 1.240 76 Sn 1000 0 0 1000 2.4 2.41.168 1.201 77 Sn 0 1000 0 1000 2.4 2.6 1.169 1.196 78 Sn 0 1000 1000 02.7 2.8 1.167 1.240 79 Sn 0 1000 1000 1000 2.6 2.5 1.189 1.240 80 Sn1000 1000 1000 0 2.7 2.6 1.185 1.240 81 Sn 1000 1000 0 1000 2.5 2.61.172 1.200 82 Sn 1000 0 1000 1000 2.3 2.6 1.186 1.241 83 Sn 1000 10001000 1000 2.4 2.5 1.188 1.241 84 Zn—In 0 0 0 0 4.9 7.1 1.171 1.199 85Zn—In 1000 0 0 0 2.6 2.7 1.167 1.197 86 Zn—In 0 1000 0 0 2.9 3.0 1.1881.200 87 Zn—In 0 0 1000 0 2.6 5.0 1.166 1.186 88 Zn—In 0 0 0 1000 2.65.0 1.168 1.197 89 Zn—In 1000 1000 0 0 2.5 2.6 1.186 1.239 90 Zn—In 10000 1000 0 2.5 2.7 1.169 1.200 91 Zn—In 1000 0 0 1000 2.4 2.7 1.168 1.19992 Zn—In 0 1000 0 1000 2.5 2.5 1.168 1.237 93 Zn—In 0 1000 1000 0 2.62.9 1.188 1.241 94 Zn—In 0 1000 1000 1000 2.5 2.5 1.187 1.241 95 Zn—In1000 1000 1000 0 2.5 2.6 1.169 1.200 96 Zn—In 1000 1000 0 1000 2.7 2.61.187 1.240 97 Zn—In 1000 0 1000 1000 2.4 2.6 1.187 1.239 98 Zn—In 10001000 1000 1000 2.5 2.6 1.188 1.240

TABLE 22 Characteristics of cell with NaOH electrolyte Self-dishchargeClosed circuit Concentration of inhibitor rate % voltage V Experi- Kindppm A part- A part- mental of Indium Lead barium Fresh discharge Freshdischarge No. plating sulfate oxide hydroxide POERA cell cell cell cell99 — 0 0 0 0 5.5 9.6 1.157 1.181 100 In 0 0 0 0 4.0 5.5 1.167 1.194 101In 1000 0 0 0 2.3 2.4 1.169 1.199 102 In 0 1000 0 0 2.2 2.5 1.169 1.198103 In 0 0 1000 0 2.2 4.7 1.185 1.199 104 In 0 0 0 1000 2.2 4.8 1.1661.184 105 In 1000 1000 0 0 2.1 2.3 1.169 1.199 106 In 1000 0 1000 0 1.92.2 1.188 1.240 107 In 1000 0 0 1000 1.9 2.2 1.168 1.200 108 In 0 1000 01000 2.1 2.4 1.167 1.199 109 In 0 1000 1000 0 2.2 2.4 1.169 1.238 110 In0 1000 1000 1000 1.8 1.9 1.189 1.240 111 In 1000 1000 1000 0 2.4 2.21.187 1.241 112 In 1000 1000 0 1000 2.2 2.1 1.171 1.202 113 In 1000 01000 1000 2.0 2.2 1.186 1.240 114 In 1000 1000 1000 1000 2.0 2.0 1.1881.240 115 Sn 0 0 0 0 4.4 6.4 1.169 1.195 116 Sn 1000 0 0 0 2.5 2.2 1.1691.200 117 Sn 0 1000 0 0 2.5 2.3 1.170 1.200 118 Sn 0 0 1000 0 2.4 4.71.189 1.200 119 Sn 0 0 0 1000 2.3 4.7 1.167 1.184 120 Sn 1000 1000 0 02.2 2.1 1.169 1.196 121 Sn 1000 0 1000 0 2.1 2.3 1.188 1.240 122 Sn 10000 0 1000 1.9 2.1 1.169 1.200 123 Sn 0 1000 0 1000 2.2 2.3 1.168 1.198124 Sn 0 1000 1000 0 2.5 2.4 1.169 1.240 125 Sn 0 1000 1000 1000 2.4 2.21.190 1.240 126 Sn 1000 1000 1000 0 2.4 2.3 1.186 1.241 127 Sn 1000 10000 1000 2.3 2.4 1.174 1.199 128 Sn 1000 0 1000 1000 2.0 2.4 1.186 1.241129 Sn 1000 1000 1000 1000 2.1 2.2 1.89  1.241 130 Zn—In 0 0 0 0 4.6 6.71.172 1.201 131 Zn—In 1000 0 0 0 2.3 2.4 1.169 1.198 132 Zn—In 0 1000 00 2.7 2.5 1.188 1.201 133 Zn—In 0 0 1000 0 2.4 4.8 1.168 1.187 134 Zn—In0 0 0 1000 2.3 4.8 1.170 1.197 135 Zn—In 1000 1000 0 0 2.1 2.4 1.1881.240 136 Zn—In 1000 0 1000 0 2.2 2.4 1.170 1.199 137 Zn—In 1000 0 01000 2.2 2.5 1.169 1.199 138 Zn—In 0 1000 0 1000 2.2 2.2 1.167 1.236 139Zn—In 0 1000 1000 0 2.1 2.6 1.187 1.243 140 Zn—In 0 1000 1000 1000 2.32.0 1.187 1.242 141 Zn—In 1000 1000 1000 0 2.3 2.4 1.168 1.201 142 Zn—In1000 1000 0 1000 2.2 2.4 1.189 1.241 143 Zn—In 1000 0 1000 1000 2.2 2.41.187 1.240 144 Zn—In 1000 1000 1000 1000 2.3 2.3 1.187 1.241

The inhibitor concentration in the table indicates a value with respectto the zinc weight. The measurement of the self-discharge rate wasperformed after maintaining at 60° C. for 20 days said to be equivalentto 1 year. The self-discharge rate after partial discharge was measuredafter maintaining at 60° C. for 20 days after 50% depth discharge(partial discharge). The closed circuit voltage was measured at −10° C.before discharge and after partial discharge.

As compared with the Examples in which no inhibitor was added (ExampleNo. 54, 69 and 84 in Table 21 and Example No. 100, 115 and 130 in Table22), the Examples added with the inhibitor have small self-dischargerates. With respect to the partial discharge, in the case of theExamples added with one of the type for coating the collector and thezinc surface such as indium sulfate and lead monoxide, theself-discharge rate is improved. It is apparent that the closed circuitvoltage is high for the Examples added with barium hydroxide. It isunderstood from the table that when the inhibitor of the coating typeand barium hydroxide are added, the self-discharge rate beforedischarge, the self-discharge rate after partial discharge, and theclosed circuit voltage are improved. In the present experiment, abehavior that the closed circuit voltage after partial discharge becomeshigher than that before discharge has been presented which is oppositeto a case using mercurated zinc. The cause thereof is now underinvestigation.

The plating of the negative electrode can was performed in the samemanner as Example 25, and results for each film thickness of 0.3 μm havebeen shown. There was little difference in the result even when thosehaving a film thickness of 0.1-1 μm were used.

Embodiment 28

Further, with a battery manufactured using an electrolyte of the KOHtype and a negative electrode can applied with indium plating, theself-discharge rate corresponding to the one after 1 year and theself-discharge rate after partial discharge with respect to theinhibitor concentration were measured.

Results are shown in FIGS. 17 and 18. Provided that the practical rangeis not more than about 3% of the self-discharge rate, according to FIG.17, it has been found to be effective for indium sulfate of 50-5000 ppm,for lead monoxide of 20-5000 ppm, for barium hydroxide of not less than50 ppm, and for polyoxyethylene alkylamide of not less than 5 ppm as theconcentration with respect to zinc.

With respect to the self-discharge rate after 50% depth discharge,according to FIG. 18, it was effective for indium sulfate of 50-5000ppm, and for lead monoxide of 20-5000 ppm. After partial discharge, theeffect is not so much for barium hydroxide and polyoxyethylenealkylamide. In order to lower the self-discharge rate after partialdischarge, it has been found to be effective to combine and use indiumsulfate or lead monoxide and barium hydroxidepolyoxyethylene alkylamide.However, it is desirable that in the combined use polyoxyethylenealkylamide is not more than 1000 ppm. The result has been shown in thecase of indium sulfate for indium compounds, however, other compoundswere also effective when used in substantially the same concentrationrange. In addition, even when an electrolyte solution of the NaOH typeor other negative electrode can plating were used, the concentrationrange of the inhibitor exhibiting the effect was substantially the same.

Embodiment 29

Trial production of batteries was performed in the same manner asExample 27 by changing the zinc composition. Using an electrolytesolution of the KOH type and plating indium onto a negative electrodecan, an inhibitor was added comprising 1000 ppm of indium sulfate, leadmonoxide, barium hydroxide and polyoxyethylene alkylamide with respectto zinc. Results are shown in Table 23.

TABLE 23 Characteristics of cell with KOH electrolyte Self-dischargeClosed circuit rate % voltage V Experi- Concentration of metal A part- Apart- mental added to zinc ppm Fresh discharged Fresh discharged No. PbBi In Al Ca cell cell cell cell 145 500 — — — — 2.9 2.8 1.186 1.200 146500  50 — — — 2.8 2.8 1.187 1.235 147 500 — — 250  — 2.8 2.7 1.186 1.235148 500 500 500 — — 2.3 2.5 1.186 1.234 149  10 100 515 30 — 2.7 2.71.188 1.222 150  23 240 — — — 2.9 2.9 1.189 1.200 151  28 240 1780  — —2.5 2.6 1.189 1.240 152 — 140 480 — — 2.4 2.6 1.185 1.239 153 — 130 50030 — 2.4 2.4 1.186 1.238 154 — 130 500 — 50 2.3 2.4 1.188 1.236

It is apparent that the self-discharge rate is included in a practicalrange of not more than 3% in the compositions of additives defined inthe claims. In order to lower the self-discharge rate, it is desirableto form an alloy of several species.

In Examples 30-31, results of evaluation mainly for combinations withgelling agents are shown.

Embodiments 30

Before practically manufacturing batteries, the effect of the presentinvention was confirmed in a form of a hydrogen gas generation test. Thetest was performed using a combination of zinc powder, a gelling agentof the present invention, barium hydroxide and a copper plate of thesame material as that of the collector. Into a specially prepared testtube having a volume of 25 ml graduated to determine the gas generationamount there was added 2 g of zinc powder containing 500 ppm of each ofbismuth, indium and lead manufactured by the atomization method. Anelectrolyte solution to be tested was added thereto and heated to 60°C., and the volume of generated hydrogen gas was measured for 7 days.The gelling agent was added by 1.5% with respect to zinc. Using 2 g ofzinc powder and 5 copper pieces of the same material as the collectorhaving a surface area of 0.6 cm² and a thickness of 0.1 mm together soas to provide the same ratio of the negative electrode zinc weight tothe negative electrode collector surface area of the battery, the gasgeneration was measured in the same manner. The number of testrepetitions was 6, and an average value thereof was used as a result.

The electrolyte solution was prepared by providing a base solution inwhich potassium hydroxide was 30% by weight and zinc oxide was added upto approximate saturation in the case of the potassium hydroxide type,or a base solution in which sodium hydroxide was 25% by weight and zincoxide was added up to approximate saturation in the case of the sodiumhydroxide type, and barium hydroxide was added thereto. Barium hydroxidewas made by Wako Pure Chemical Industries., Ltd., CMC was No. 1260 andNo. 1380 made by Daicel Chemical Industries, Ltd., and PAS was a reagentmade by Wako Pure Chemical Industries., Ltd. and Rheogic 250H made byNihon Pure Chemicals Co., Ltd. The added amount of barium hydroxide was0-50000 ppm with respect to the electrolyte solution. Results are shownfor the hydrogen generation amount in Table 24.

TABLE 24 Hydrogen evolution rate Amount of Hydrogen Experi- Kind ofadded barium evolution mental electro- Geled Copper hydroxide rate No.lyte agent pieces ppm μl/g/day 1 KOH CMC 1260 none 0 35.71 2 KOH CMC1380 none 0 30.43 3 KOH PAS WAKO none 0 22.12 4 KOH PAS 250H none 013.58 5 KOH CMC 1260 none 1000 24.73 6 KOH CMC 1380 none 1000 19.39 7KOH PAS WAKO none 1000 8.65 8 KOH PAS 250H none 1000 6.82 9 KOH CMC 1260include 1000 215.31 10 KOH CMC 1380 include 1000 189.56 11 KOH PAS WAKOinclude 1000 99.49 12 KOH PAS 250H include 1000 87.12 13 KOH none none50000 2.02 14 KOH none none 10000 1.99 15 KOH none none 5000 2.01 16 KOHnone none 1000 2.10 17 KOH none none 500 2.24 18 KOH none none 100 2.5519 KOH none none 0 3.19 20 KOH none include 50000 238.42 21 KOH noneinclude 10000 31.54 22 KOH none include 1000 46.37 23 NaOH none include100 84.25 24 NaOH none include 0 516.63 25 NaOH none none 50000 1.90 26NaOH none none 10000 1.95 27 NaOH none none 5000 2.00 28 NaOH none none1000 2.02 29 NaOH none none 500 2.12 30 NaOH none none 100 2.31 31 NaOHnone none 0 3.46 32 NaOH none include 50000 25.13 33 NaOH none include10000 27.58 34 NaOH none include 1000 31.49 35 NaOH none include 10095.61 36 NaOH none include 0 252.89

The unit is μl/g/day. According to the result in Table 24, it isunderstood that one added with barium hydroxide has a small hydrogengeneration.amount irrespective to comparison in the gelling agent type,the zinc powder simple substance and the zinc powder+copper piece, andthe electrolyte solution type. The gas generation is also small due toPAS being a cross-linked type acrylic water-soluble resin with respectto the gelling agent type.

It is apparent that the combination of PAS as a cross-linked typeacrylic water-soluble resin and barium hydroxide is especially good.When the added amount of barium hydroxide was not less than 500 ppm,there was supersaturation, so that the electrolyte solution in a turbidstated was used. In addition, barium hydroxide was added to theelectrolyte solution in Example 30, however, the same effect wasobtained even when the whole amount was added to powdery zinc.

Embodiment 31

A button type silver oxide battery of the SR621 size was prepared. As anegative electrode can a collector applied with tin plating of 0.1 μmwas used. The zinc was the one used in Example 30, Rheogic 250H as across-linked type acrylic water-soluble resin for a gelling agent, and apotassium hydroxide 30% by weight solution or a sodium hydroxide 25% byweight solution added with zinc oxide up to approximate saturationrespectively for an electrolyte solution. The added amount of thegelling agent was 1.5% with respect to zinc, and the added amount ofbarium hydroxide was 0-50000 ppm with respect to zinc. As Conventionalexample, a battery was manufactured in which CMC 1260# was used for thegelling agent with no barium hydroxide added. Evaluation results ofelectric characteristics are shown in the discharge index in Table 25.

TABLE 25 Characteristics of cell Amount of Comparison Hydrogen Experi-Kind of added barium of evolution mental electro- hydroxide dischargerate No. lyte ppm capacity μl/g/day 1 KOH 50000 97 0.208 2 KOH 10000 1000.205 3 KOH 1000 103 0.227 4 KOH 100 1023 0.708 5 KOH 10 102 1.693 6 KOH0 101 1.812 Conventional KOH 0 100 2.513 7 NaOH 50000 98 0.192 8 NaOH10000 101 0.185 9 NaOH 1000 102 0.183 10 NaOH 100 102 0.228 11 NaOH 10101 0.342 12 NaOH 0 101 0.549 Conventional NaOH 0 100 0.712

The electric characteristics were measured by the direct current methodwith a load resistance of 200 Ω when the electrolyte solution was thepotassium hydroxide type or the pulse method with a load resistance of 2kΩ when it was the sodium hydroxide type. In either case, Theconventional example had a discharge index of 100. As being apparentalso from the result, one in which the gelling agent of the presentinvention and the cross-linked type acrylic water-soluble resin wereused and barium hydroxide was added had a good discharge performance ascompared with the conventional example.

Using a gasket of polypropylene specially prepared for allowing hydrogento penetrate, a button type silver oxide battery was manufactured in thesame manner. As a gelling agent, 1.5% of Rheogic 250H being across-linked type acrylic water-soluble resin was used with respect tozinc. Barium hydroxide were tested with a concentration of 10 ppm to 5ppm to 5% with respect to a weight of zinc. Ten pieces of themanufactured silver oxide batteries were placed in a vessel made ofglass filled with liquid paraffin in a high temperature tank, acollecting tube having graduations at an upper portion was attached, andthe amount of generated hydrogen was measured. This state was maintainedat 60° C. for 20 days, and the hydrogen gas generation amount after 20days was investigated. Evaluation results are shown in the hydrogen gasgeneration amount in Table 25, and a result of a case using a potassiumhydroxide 30% by weight solution as the electrolyte solution is shown inFIG. 19. According to the figure, it is apparent that barium hydroxideworks effectively at 100 ppm to 1%.

Using a gasket made of polyproylene was returned to one made of nylon, abutton type silver oxide battery was manufactured in a range of bariumhydroxide concentration of 100 ppm to 1% which had less gas generation.Ten pieces of the manufactured batteries were placed in a vessel made ofglass filled with liquid paraffin in a high temperature tank in the samemanner, and a collecting tube for generating hydrogen gas was attachedto an upper portion. Hydrogen gas generation, expansion of the batterycan and liquid leakage were not observed after 20 days at 60° C.

The hydrogen gas generation amount in the actual battery has a valuesmaller than that of the hydrogen gas generation amount in theexperiment in Example 30. For this fact, it is considered that thecopper piece used in Example 30 is different from the structure of anactual collector, a part of generated hydrogen gas has been consumed bythe reduction of silver oxide and the like. The method in Example 30 isdifferent in the amount order of hydrogen gas generation, but it issufficient as a method for observing substituted characteristics forpredicting hydrogen generation in an actual battery.

In accordance with Examples 32-35, the effect of a case in which thecollector is provided with a zinc alloy layer and evaluation results ofa case in which the alkaline battery of the present invention is usedfor a clock or watch are shown.

Before actually investigating characteristics using batteries, aspecially prepared test tube was used to investigate what amount ofhydrogen gas was generated from a plated copper plate (the same materialas a collector). The method therefor will be described hereinafter.

Into a specially prepared test tube having a volume of 25 ml graduatedto determine the gas generation amount, there were previously added 2 gof zinc powder containing 500 ppm each of bismuth, indium and leadmanufactured by the atomization method, and a copper piece being thesame material as the collector and having an area of 0.6 cm² and athickness of 0.1 mm being applied with the plating of the presentinvention. An electrolyte solution was added thereto and heated to 60°C., and the volume of generated hydrogen gas was measured for 7 days.The number of test repetitions was 10, and an average value thereof wasused as a result. As the electrolyte solution there was used a solutionin which potassium hydroxide was 30% by weight and zinc oxide was addedup to approximate saturation in the case of the potassium hydroxidetype, and a solution in which sodium hydroxide was 25 by weight and zincoxide was added up to approximate saturation in the case of the sodiumhydroxide type.

Embodiment 32

The hydrogen generation from zinc and a copper piece coated with theelectric plating and the substitution plating was measured. Four kindsof plating treatments onto the copper piece were performed. Conditionsare shown hereinafter.

=Contact Plating (zinc-indium)

method: | contact plating: A copper piece and zinc were placed into thefollowing plating bath heated to 60° C. and left for 1 hour.

plating bath: KOH 30%, ZnO saturation, indium sulfate 0-3000 ppm

temperature: 60° C.

plating film thickness: Adjustment was made depending on time. Thethickness was determined from weights before and after the plating.

=Contact Plating (zinc-lead)

method: contact plating: A copper piece and zinc were placed into thefollowing plating bath heated to 60° C. and left for 1 hour.

plating bath: KOH 30%, ZnO saturation, lead oxide 0-3000 ppm

temperature: 60° C.

plating film thickness: Adjustment was made depending on time. Thethickness was determined from weights before and after the plating.

=Electric Plating (cyanide type)

method: A copper piece was clamped in a net made of copper to allow acurrent to flow, and plating was performed. The copper piece wassuitably moved so as not to make a portion not subjected to plating.

plating bath: zinc cyanide 70 g/l, sodium cyanide 50 g/l, sodiumhydroxide 100 g/l, indium cyanide 0-3000 ppm

temperature: 25° C.

current density: 5 A/dm²

plating film thickness: Adjustment was made depending on time. Thethickness was determined from weights before and after the plating.

=Electric Plating (acidic)

method: A copper piece was clamped in a net made of copper to allow acurrent to flow, and plating was performed. The copper piece wassuitably moved so as not to make a portion not subjected to plating.

plating bath: zinc sulfate 240 g/l, sodium sulfate 30 g/l, sodiumacetate 15 g/l, indium sulfate 0-3000 ppm

temperature: 25° C.

current density: 2 A/dm²

plating film thickness: Adjustment was made depending on time. Thethickness was determined from weights before and after the plating.

A copper piece subjected to each treatment, zinc powder and anelectrolyte solution were added in a specially prepared test tube, andthe amount of hydrogen gas generated therefrom was investigated. It issupposed that the larger the hydrogen gas generation, the larger is theself-discharge in an actual battery.

TABLE 26 Hydrogen evolution rate in KOH electrolyte Hydrogen evolutionrate (μl/g/day) Experi- Condition of plating vs concentration ofadditive in mental Kind of plating solution (ppm) No. plating Additive 010 100 1000 3000 1 Contact plating Indium sulfate 16.92 14.29 10.7112.14 8.57 2 Contact plating PbO ↑ 13.28 12.96 96.34 120.36 3Electroplating Indium cyanide ↑ 15.47 13.22 10.25 10.81 4 ElectroplatingIndium sulfate ↑ 18.24 15.26 15.13 7.41

TABLE 27 Hydrogen evolution rate in NaOH electrolyte Hydrogen evolutionrate (μl/g/day) Experi- Condition of plating vs concentration ofadditive in mental Kind of plating solution (ppm) No. plating Additive 010 100 1000 3000 5 Contact plating Indium sulfate 480.23 13.00 10.1711.53 7.11 6 Contact plating PbO ↑ 12.75 11.28 90.56 102.31 7Electroplating Indium cyanide ↑ 14.54 12.82 9.43 9.84 8 ElectroplatingIndium sulfate ↑ 18.06 14.19 14.98 6.45

In Table 26, the hydrogen generation amount in the KOH type electrolytesolution with respect to the copper piece plated with each concentrationof lead oxide is shown. In Table 27, the result in the NaOH typeelectrolyte solution is shown.

According to Tables 26 and 27, it is understood that the hydrogen gasgeneration can be greatly suppressed as by adding a little amount ofindium compound and lead oxide of about 10 ppm into the platingsolution, and forming an alloy of the plating film as compared with noaddition. However, in the case of addition of lead oxide in a highconcentration, needle-like lead becomes deposited on the plating film,and the hydrogen gas generation is deteriorated.

When the copper piece subjected to the substitution plating wasquantitatively measured by the Auger spectroscopic analysis, it wasfound that about 0.3% of indium existed in the plating film in the caseof adding indium sulfate in an amount of 1000 ppm, and about 0.1% ofindium existed in the case of adding indium sulfate in an amount of 100ppm. In the case of the plating film manufactured by adding indiumsulfate to the plating solution by not more than 100 ppm, it wasimpossible to measure indium as being not more than the detection limit.However, it is considered that the hydrogen gas generation suppressingeffect is obtained by the inclusion of an extremely minute amount ofindium into the plating film. For other kinds of plating, it isconsidered that the hydrogen gas generation suppressing effect is alsoobtained because indium and lead are deposited in zinc to lower thehydrogen overvoltage of zinc.

TABLE 28 Hydrogen evolution rate in KOH electrolyte Experi- Condition ofplating Hydrogen evolution rate (μl/g/day) mental Kind of vs platingthickness (μm) No. plating Additive 0 0.015 0.074 0.082 0.152 0.222 9Contact plating Indium sulfate 516.9 11.79 7.50 13.21 8.93 8.75

TABLE 29 Hydrogen evolution rate in NaOH electrolyte Experi- Conditionof plating Hydrogen evolution rate (μl/g/day) mental Kind of vs platingthickness (μm) No. plating Additive 0 0.015 0.074 0.082 0.152 0.222 10Contact plating Indium sulfate 480.2 12.36 6.23 6.02 7.71 7.11

In Tables 28 and 29, the hydrogen gas generation amount with respect tothe film thickness is shown in the substitution plating added with 1000ppm of indium sulfate. According to Tables 28 and 29, it is apparentthat the effect is provided from 0.015 μm as being fairly thin.

Embodiment 33

Next, trial production of a battery was actually performed to confirmthe effect on the negative electrode can.

Into a positive electrode can there were added a part of an electrolytesolution 116 mg of a pellet (silver oxide content of 98%) made by addingsilver oxide molded with a combined agent, a separator of polyethyleneand a separator of cellophane. Next, a gasket of nylon was pushed andfitted into the positive electrode can, an impregnating agent, a gellingagent, and 30 mg of zinc powder were added, and the remainder of theelectrolyte solution optionally provided with an inhibitor was addeddropwise. Thereafter, a negative electrode can was placed and sealed tomanufacture 100 pieces for each kind of button type silver oxidebatteries.

As the zinc powder, one containing 500 ppm of bismuth, 500 ppm of indiumand 500 ppm of lead manufactured by atomization was used. The platingonto the negative electrode can was performed in the same manner asExample 32.

The self-discharge rate with respect to the type of the plating onto thenegative electrode can is shown in Tables 30 and 31. The measurement ofthe self-discharge rate was performed after maintaining 60° C. for 20days which is said to be equivalent to 1 year.

TABLE 30 Self-discharge rate of cell with KOH electrolyte Self-dischargeExperi- Condition of plating rate mental Kind of after 1 year No.plating Additive storage % 11 none — 5.8 12 Contact plating Indiumsulfate 2.5 13 Contact plating PbO 2.8 14 Electroplating Indium cyanide2.4 15 Electroplating Indium sulfate 2.4

TABLE 31 Self-discharge rate of cell with NaOH electrolyteSelf-discharge Experi- Condition of plating rate mental Kind of after 1year No. plating Additive storage % 16 none — 5.5 17 Contact platingIndium sulfate 2.2 18 Contact plating PbO 2.5 19 Electroplating Indiumcyanide 2.1 20 Electroplating Indium sulfate 2.2

According to Tables 30 and 31, it is understood that the self-dischargerate can be suppressed by using the plated negative electrode can of thepresent invention as compared with the negative electrode can notsubjected to plating.

In this case, results are shown in which the added amount of the indiumcompound into the plating solution was 1000 ppm, the added amount oflead oxide was 100 ppm, and each film thickness was 0.1 μm. There waslittle difference in the result even when those having a film thicknessof 0.013 μm were used. In addition, equivalent effects were obtained inranges in which the amount of the indium compound added into the platingsolution was 10-3000 ppm, and the amount of lead oxide added was 10-100ppm. When the same test was performed for potassium stannate and sodiumstannate, equivalent effects were obtained in a range of the addingamount of 10-3000 ppm. In addition, equivalent effects were obtainedeven when plating solutions mixed and added with indium compounds, leadoxide, potassium stannate and sodium stannate in these concentrationranges have been used.

Embodiment 34

A test was performed for the impurity shielding effect of the platingfilm.

Plating was performed for a negative electrode can having the SR521 sizein which iron type foreign matters had adhered to the collector surfaceduring press processing causing deficiency in gas generation. Thedeficiency in gas generation may become a cause of expansion andexplosion when a battery is made, which can be confirmed by instant gasgeneration after adding an electrolyte solution and several zinc powderparticles of about 100 μm to a concave surface at the copper side as thecollector of the negative electrode can. This is due to the fact thatzinc serves as an anode and iron having a lower hydrogen overvoltageserves as a cathode to generate hydrogen. The plating was performed bysubstitution plating using a barrel. Conditions are describedhereinafter.

=Contact Plating (zinc-indium)

method: contact plating: Using a barrel, a negative electrode can and azinc piece were added into the following plating solution heated to 60°C. to perform plating.

negative electrode can: SR521 size, about 1000 pieces

zinc piece: 3×3×0.1, about 1500 sheets

plating solution: KOH 30%, ZnO saturation, indium sulfate 0-300 ppm

temperature: 60° C.

time: 5, 15 and 30 minutes

plating film thickness: The thickness was measured from weights of acopper plated added as a dummy before and after the plating.

The film thickness against time was 0.041 μm for 5 minutes, 0.090 μm for15 minutes, and 0.148 μm for 30 minutes. 100 pieces were picked outrespectively, and the confirmation of gas generation was performed. As aresult, the gas generation was found in 78 pieces out of 100 pieces inthe case of those subjected to plating for 5 minutes. No gas generationwas found in those subjected to plating for 15 and 30 minutes. Accordingto this fact, it has been found that a plating thickness of about 0.1 μmhas shielding effect for impurities.

Embodiment 35

Next, results are shown for a case in which the shaping into a negativeelectrode can was performed after plating onto a hoop material insteadof the direct negative electrode can plating as done in Example 33. Inthis case, although there is an advantage that the plating can be madethick by the electric plating, however, there is a problem thatdeficiency is apt to be caused in a soft plating film by mechanicalprocessing. Plating conditions are shown hereinafter.

Electric Plating (cyanide type)

method: The nickel side of a hoop material was cladded with three-layersof nickel, stainless and copper was subjected to masking, and platingwas performed onto the copper side.

plating bath: zinc cyanide 70 g/l, sodium cyanide 50 g/l, sodiumhydroxide 100 g/l, indium cyanide 1000 ppm

bath temperature: 25° C.

current density: 5 A/dm²

plating film thickness: Adjustment was made depending on time. Thethickness (adjustment of the feed speed of the hoop material) wasdetermined by embedding in a resin and taking a picture using an opticalmicroscope.

Those having a film thickness of 1, 2, 3, 4, 7 or 10 μm weremanufactured. Negative electrode cans of 100 pieces were manufacturedusing each hoop material plated with a zinc alloy of each filmthickness. The number of negative electrode cans in which the coppersurface became exposed by processing was investigated. Results are shownin Table 7.

According to the result, it is apparent that the copper surface ceasesto be exposed in the case of not less than 3 μm.

The negative electrode cans for each film thickness were used to performtrial production of 100 pieces of batteries respectively with an NaOHtype electrolyte solution in the same manner as Example 33.

TABLE 32 Number of anode cap with generated pinhole and self-dischargerate Plating 1 2 3 4 7 10 Cell using thickness (μm) analgamated Numberof 8 3 0 0 0 0 zinc anode cap with generated pinhole Initial capacity23.2 23.3 23.4 23.6 24.1 24.8 23.1 (mAh) Capacity after 21.2 21.7 22.022.7 23.0 23.8 22.6 2 years storage (mAh) Self-discharge 4.4 3.5 2.9 1.92.1 2.0  1.1 rate (%/year)

The initial capacity and the capacity corresponding to the one after 2years (after storage at 60° C. for 40 days) are shown in Table 32. Aresult of a case where mercurated zinc was used is also described at theright end in the table for the purpose of comparison. According to Table32, the plating of not more than 2 μm has a capacity smaller than thatof the case in which direct plating was performed to the negativeelectrode can in Example 33 due to deficiency in the plating film byprocessing. When the film thickness is 4 μm, the capacity after 2 yearsbecomes approximately the same as the one in which mercurated zinc isused. For example, when the battery is incorporated into a clock orwatch, the battery service life is about 2 years. In order to expect acapacity equivalent to or not less than that of a battery usingmercurated zinc after 2 years, it is necessary to plate the zinc alloyby not less than 4 μm according to Table 32. In the design of a battery,it is available that the zinc alloy plating thickness may be not lessthan 3 μm so as to have a thickness with which an aimed capacity isobtained in 2 years.

Embodiment 36

A conventional battery in which zinc having a mercuration ratio of 10%was used and a battery in which a 4 μm zinc-indium alloy was applied toa negative electrode can of the present invention by the same method asExample 35 using mercuryless zinc were actually installed inwristwatches, and a carrying test was performed to measure the number ofdays until the watch stopped. The test was done for each 10 pieces.

TABLE 33 Cell life by watch Cell using zinc without mercury Cell usingand plated anode cap amalgamated zinc (plating thickness:4 μm) Cell life(days) 751.1 758.3 σ 14.8 23.6

Results are shown in Table 33. The number of days until the watchstopped was substantially the same, and coming off with the capacity notbeing lowered even in the case of no mercury.

As shown in Example 35, it is apparent that when using as a standard afilm thickness, in which the capacity after 2 years in the accelerationtest becomes the same as that of the battery using mercurated zinc, itis possible to obtain a capacity equivalent to the one in whichmercurated zinc is used also when used in an actual clock or watch.

Namely, in the design of a battery, the zinc alloy plating thickness maybe made to be not less than 3 μm so as to provide a thickness with whichan aimed capacity is obtained in 2 years. For example, provided that theweight of zinc in the battery using mercurated zinc of an aimed capacity(excluding an amount of mercury) is W0, the self-discharge rate/year isSD0, the weight of zinc in the battery using mercuryless zinc to bedesigned is W0 (the same as mercurated zinc), the self-discharge rate isSD1, the area of the collector is S, and the specific gravity of zinc is7.13, the film thickness D1 of the zinc alloy may be as follows:

D1=(W0×(1−2×SD0)/(1−2×SD1)−W0)/7.13/S

In the present Examples 35 and 36, it has been described that the cladmaterial is plated with the zinc-indium alloy of not less than 3 μm,however, as shown in Examples 32 and 33, approximately the same effectis obtained provided that the zinc alloy is an alloy containing zinc asan essential element and containing one or more species selected fromindium, lead and tin as a selective element. In addition, it isunderstood that the same effect is obtained even when the formationmethod of the zinc alloy layer is another method. For example, methodscladding a zinc alloy with one more layer, or using dry plating or flamecoating and the like are applicable.

In addition, the effect of the invention is not deteriorated even whenelements which raise the hydrogen overvoltage of the zinc alloy such asbismuth, gallium, aluminum, calcium and the like exist in the zinc alloylayer containing indium or lead. Depending on the way of addition,further self-discharge suppressing effects can be expected.

As also described in Examples hereinbefore, according to the presentinvention, it is possible to manufacture the alkaline battery in whichthe generation of hydrogen is suppressed without deteriorating batterycharacteristics. This is especially effective for coin-type or buttontype alkaline batteries which require high performance but are sensitiveto gas generation.

In addition, with respect to the zinc alloy plating onto the collectorof the present invention, when it is used for minute discharge forclocks or watches or the like, it is possible to achieve a capacitywhich is equivalent to or not less than those of batteries in whichmercurated zinc is used. Further, when clocks or watches carrying thealkaline batteries of the present invention discarded, the environmentis never polluted because mercury as an environmental pollutionsubstance is not contained. Similarly, when an electronic apparatuscarrying the alkaline batteries are discarded, the environment is neverpolluted because mercury as an environmental pollution substance is notcontained.

What is claimed is:
 1. An alkaline battery comprising: a negativeelectrode having an active material comprised of mercuryless zinc powdercontaining a gelling agent and one or more metals selected from thegroup consisting of 0.001-0.5% by weight of gallium 0.005-0.5% by weightof indium 0.0001-0.5% by weight of lead 0.005-0.5% by weight of bismuth.0.001-0.5% by weight of aluminum and 0.001-0.5% by weight of calcium; acurrent collector having an outer surface coated with a layer of zinc ora metal having a hydrogen overvoltage higher than that of zinc; and anelectrolyte containing an indium compound selected from the groupconsisting of indium sulfate, indium sulfamate and indium chloride. 2.An alkaline battery as claimed in claim 1; wherein the gelling agentcomprises a cross-linking polyacrylic water-absorbing polymer alone orin combination with other gelling agents.
 3. An alkaline battery asclaimed in claim 1; wherein the indium Compound is selected from thegroup consisting of indium sulfate, indium sulfamate, indium chlorideand indium hydroxide.
 4. An alkaline battery as claimed in claim 1;wherein the outer surface of the current collector is coated with alayer of a zinc-indium alloy.
 5. In combination with an electronicapparatus: an alkaline battery for supplying power to the electronicapparatus, the alkaline battery comprising a negative electrode havingan active material comprised of mercuryless zinc powder containing agelling agent, a current collector having an outermost surface coatedwith a layer of zinc or a metal having a hydrogen overvoltage higherthan that of zinc, and an electrolyte containing an indium compoundselected from the group consisting of indium sulfate, indium sulfamateand indium chloride, wherein the mercuryless zinc powder contains one ormore metals selected from the group consisting of 0.001-0.5% by weightof gallium, 0.005-0.5% by weight of indium, 0.0001-0.5% by weight oflead, 0.005-0.5% by weight of bismuth, 0.001-0.5% by weight of aluminumand 0.001-0.5% by weight of calcium.
 6. A combination as claimed inclaim 5; wherein the outer surface of the current collector is coatedwith a layer of a zinc-indium alloy.
 7. An alkaline battery comprising:a negative electrode having an active material comprised of mercurylesszinc powder containing a gelling agent; a current collector having anouter surface coated with a layer of zinc or a metal having a hydrogenovervoltage higher than that of zinc; and an electrolyte containingbarium hydroxide and polyoxyethylene alkylamide.
 8. An alkaline batteryas claimed in claim 7; wherein the mercuryless zinc powder contains oneor more metals selected from the group consisting of 0.001-0.5% byweight of gallium, 0.005-0.5% by weight of indium, 0.0001-0.5% by weightof lead, 0.005-0.5% by weight of bismuth, 0.001-0.5% by weight ofaluminum and 0.001-0.5% by weight of calcium.
 9. An alkaline battery asclaimed in claim 7; wherein the outer surface of the current collectoris coated with a layer of a zinc-indium alloy.
 10. An alkaline batterycomprising: a negative electrode having an active material comprised ofmercuryless zinc powder containing a gelling agent and one or moremetals selected from the group consisting of 0.001-0.5% by weight ofgallium, 0.005-0.5% by weight of indium, 0.0001-0.5% by weight of lead,0.005-0.5% by weight of bismuth, 0.001-0.5% by weight of aluminum and0.001-0.5% by weight of calcium; a current collector having an outersurface coated with a layer of zinc or a metal having a hydrogenovervoltage higher than that of zinc; and an electrolyte containingindium sulfate.
 11. An alkaline battery as claimed in claim 10; whereinthe outer surface of the current collector is coated with a layer of azinc-indium alloy.
 12. An alkaline battery as claimed in claim 10;wherein the layer of zinc or metal having a hydrogen overvoltage higherthan that of zinc comprises one or more metals or alloys selected fromthe group consisting of zinc, indium, tin and lead.